NCI High Risk Research Articles

Title: Risk Factors and Natural History of Vincristine Induced Neuropathy on UKALL 2011: A Randomised Controlled Trial of the Effect of Omitting Vincristine Pulses

Introduction UKALL 2011 is a randomised study recruiting children and young adults (up to 25) with Acute Lymphoblastic Leukaemia (ALL) or Lymphoblastic Lymphoma (LBL). One of the aims of the trial was to reduce maintenance morbidity by randomising to Vincristine (VCR)/dexamethasone pulses or not. Results of this randomisation were presented at ASH 2022. In a sub-study, we also aimed to determine the natural history of vincristine induced neuropathy (VIN), including patients randomised to vincristine in maintenance or not and to determine pharmacogenomic risk factors for VIN. Methods Children and adolescents, aged 5-18yrs, were recruited from 5 centres in the UK. Patients were stratified by NCI risk, cytogenetics and end of induction MRD to receive Regimens A (NCI standard risk, MRD low risk), B (NCI high risk, MRD low risk) or C (Cytogenetic poor risk or MRD intermediate risk regardless of NCI risk). The maximum total number of vincristine doses was dependent on regimen and gender: females - Regimen A/B 33, Regimen C 42; males Regimen A/B 46, Regimen C 55. VIN was assessed at 7 time points (diagnosis, end of induction, delayed intensification, maintenance cycles 1,3 & 5 and end of treatment) using the Paediatric TNSr-Vincristine. The Paediatric TNSr-Vincristine assessed proximal extension of numbness, vibration, temperature sensation, muscle strength, tendon reflexes, constipation and hoarseness with each item scored from 0-4, with higher scores indicating more severe neuropathy (n=67). To assess how walking was affected, gait assessment was completed using the GAITRite® walkway-a mat embedded with several thousand electronic pressure sensors activated by mechanical pressure that captured key walking outcomes (velocity, cadence and step length) (n=46). The gait parameters were analysed and compared with age and gender matched controls enabling Z-scores comparison to normal controls. Nine candidate SNPs associated with VIN were genotyped (n=58) and were analysed against highest TNS score at any timepoint and TNS scores above and below the mean. 39 children were randomised to vincristine or not (20 vincristine vs. 19 no vincristine). We fitted linear mixed-effects regression. Predictive factors included genetics; treatment time point; post induction regime (C vs A/B). For the randomised cohort the effect of pulsed vincristine was explored. All tests were two-sided, with significance determined as p<0.05. We adjusted the effects in the model to accommodate effect of age and gender on the total neuropathy score for paediatrics. Analyses were performed using R version 4.3.1. Results Compared to diagnosis, the likelihood of VIN increased between end of induction and intensification, and then reduced over subsequent visits, but remained significantly abnormal at end of treatment (TNS incident rate ratio (IRR) 6.2 (end of induction/intensification vs diagnosis); 4.1 (end of treatment vs diagnosis); p<0.001) (Fig 1). Older children were more likely to have a higher TNS score (IRR 2.4 (p=0.003). Velocity, cadence and step length data were significantly affected compared to normal standards ( p<0.001; Figure 2). Regimen C led to a reduction in step length Z-score of a third ((L) p=0.05; (R) p=0.03)). The likelihood of a higher VIN score in patients randomised to pulsed vincristine in maintenance compared to no vincristine was borderline significant (TNS score (IRR) 1.31 with a confidence interval of 1.00-1.71 (p=0.05)).When analysed by ABCB1 haplotype, TTT/TTT carrier status (loci rs1045642, rs1128503 and rs2032582) was significantly associated with lower TNS scores (p=0.04), whilst the CEP72 TT genotype was significantly associated with TNS scores below the mean (p=0.03) in contrast to previous literature and the ABCB1 rs2032582 G allele was associated with significantly higher mean TNS scores (p=0.04) Conclusion VIN increases with intensity of vincristine treatment and does not normalise at the end of treatment. VIN led to a slower gait and shorter steps whilst removing vincristine in maintenance was associated with reduced likelihood of VIN. VIN was not strongly influenced by any single genotype in this cohort. Conflicting pharmacogenomics results could be explained by differences in ethnicity, protocol design and relatively small numbers in this analysis. Gait analysis represents a novel functional method of assessing VIN enabling comparison to normal age matched peers.

High Dose Methotrexate Does Not Reduce the Risk of CNS Relapse in Children and Young Adults with Acute Lymphoblastic Leukaemia and Lymphoblastic Lymphoma. Results of the Randomised Phase III Study UKALL 2011

Introduction UKALL 2011 randomised children and young adults (up to 25) with Acute Lymphoblastic Leukaemia (ALL) or Lymphoblastic Lymphoma (LBL). The aims were to reduce induction toxicity (R1: Short [14 days] vs Standard [28 days] dexamethasone), CNS relapse risk (R2IM: HD MTX (HDM) vs standard interim maintenance (SIM)) and maintenance morbidity (R2pulses: Vincristine (VCR)/dexamethasone pulses or not). R1 results were presented at ASH 2017 and did not show a reduction in toxicity with short dexamethasone. Results of R2IM and R2pulses are reported here. Patients and Methods Patients were stratified by NCI risk, cytogenetics and end of induction MRD to receive Regimens A (NCI standard risk, MRD low risk), B (NCI high risk, MRD low risk) or C (Cytogenetic poor risk or MRD intermediate risk regardless of NCI risk). MRD high risk (end of consolidation MRD >0.5%, n=14) were not eligible for randomisation and received off protocol therapy. R2 was a factorial randomisation stratified by factors including NCI and MRD risk groups and resulted in 4 arms: HDM with pulses, HDM without pulses, standard interim maintenance (SIM) with pulses (standard of care) and SIM without pulses. SIM was for 2 months with oral mercaptopurine/MTX, monthly pulses and single IT MTX in Regimens A and B, and 5 doses of escalating IV MTX (Capizzi) + VCR + 2 doses of Pegylated asparaginase in Regimen C. HDM was given at a dose of 5g/m2 x 4 doses 2 weeks apart, low dose 6-MP and 2 doses of Pegylated asparaginase (Regimen C only). The primary endpoint for R2IM was the CNS relapse rate (CNSR) and for R2pulses was the bone marrow relapse rate (BMR) in ALL only; non-inferiority, 5% margin at 5 years. Event Free Survival (EFS) was considered a primary endpoint for both. Results Of the 2750 patients registered on trial between April 2012 and December 2018, 1902 were randomised to R1 (closed April 2017) and 1570 to R2. Median age 5 years (IQR: 3-11), 83% B-ALL, 12% T-ALL, 1% B-LBL and 4% T-ABL, 43% NCI high risk. Median follow-up for R1 is 76 months and R1 or R2 is 72 months. Overall, we found no difference in CNSR (HR: 0.99 (0.65-1.51), p=0.97, 5-year rates: 5.6% and 5.6%), or any other endpoints for R2IM. However, there was an interaction between the R1 and R2IM randomisations (p=0.006 for EFS) with inferior outcomes for patients treated with short dexamethasone followed by HDM, particularly in those who did not receive pulses (Figure 1). Limiting analyses to patients treated with standard dexamethasone (N=995, including those that received it after closure of R1) there was a significant reduction in BMR rate with HDM (HR 0.62 (95% CI: 0.40 - 0.95) p = 0.029) and a trend for improvements in EFS and OS (HRs: 0.75 (95%CI: 0.53 - 1.04), p=0.087 and 0.61 (0.37 - 1.03), p=0.067) but no difference in CNSR. In subgroup analyses there were no significant interactions, but the effect appeared stronger for B-lineage, NCI high risk and MRD low risk patients (Figure 2). Overall, the BMR for R2pulses was non-inferior (+2.1% increase BMR at 5 years for ALL patients (95% CI: -1.4% to 4.7%), HR 1.22 (95%CI: 0.89 - 1.67). Considering all four R2 treatment arms in standard dexamethasone only, standard IM without pulses has a lower EFS, whilst there is no appreciable benefit of pulses in HDM treated patients; 5-year EFS difference: -2.8% (95% CI: -7.4% to 4.4%) and BMR (ALL): +0.4% (-6.7% to 4.3%). Conclusions HDM does not improve CNSR within a UKALL treatment backbone, but pre-specified analyses suggest it may improve BMR for some sub-groups of B-lineage patients when given following standard dexamethasone induction. Although the 'no pulses' arm was non-inferior overall for BMR, further sub-group and toxicity analyses are to be performed and will presented at the meeting. Acknowledgements Children with Cancer, Blood Cancer (grant ref 09042) and Cancer Research UK funded the trial. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Premedication and Therapeutic Drug Monitoring (TDM) for Pegaspargase: A Prospective Multicenter Multi-Ethnic Study of Pediatric and Adolescent Patients

Background: Pegaspargase (PEG) is integral in the treatment of patients with acute lymphoblastic leukemia/lymphoma (ALL/LBL). However, full exposure to all doses of PEG can be limited by hypersensitivity reactions (HSR), which necessitate a switch to alternative asparaginase formulations. Previous studies in the pediatric population evaluating the use of premedication with antihistamines (H1 and H2) to decrease the incidence of HSR have largely been retrospective and showed mixed results. We conducted the first prospective, multicenter study to evaluate the efficacy of premedicating pediatric and adolescent patients receiving PEG with H1 and H2 blockers to decrease the rate of HSR. We report on our interim analysis with a special focus on ethnic disparities in asparaginase activity and HSR. Methods: We enrolled patients with ALL/LBL treated according to a Children's Oncology Group protocol at six centers across the US. Starting with the first dose of PEG in consolidation and subsequently, patients received an H1 blocker (diphenhydramine) and an H2 blocker (ranitidine, famotidine or cimetidine) 30-60 minutes prior to every dose of PEG, which was infused over 60-120 minutes. TDM was performed at 7-10 and 14-17 days post each PEG infusion. Therapeutic asparaginase activity was defined as ≥ 0.1 IU/mL (≥100 IU/L ) at 7-10 days post infusion and greater than the lower level of quantification at 14-17 days. We observed for silent inactivation (subtherapeutic levels without symptoms) and accelerated clearance (levels below quantification at 14-17 days without symptoms). Ethnicity differences were assessed using Chi-square and independent t-tests, increased odds of HSR by GLM procedure, and average asparaginase activity across treatments using GEE analyses. Results: We report on the 74 patients enrolled from 10/2019 to 7/2021 who completed all PEG therapy at the time of analysis. The median age at diagnosis was 7.7 years [range 1.3-19.8], 63.5% were male, 90.5% had B-ALL, 35.1% were NCI High Risk (HR) at diagnosis, and 8.1% had Down Syndrome (Table 1). A majority self-identified as Hispanic ethnicity (56.8%). We noted a disparity in obesity/overweight status by ethnicity. Overall, 50.0% of Hispanics were obese (31.0%) or overweight (19.0%) compared to 12.6% of non-Hispanics (6.3% obese and 6.3% overweight), p=.007. The average body mass index (BMI, kg/m2) in Hispanic compared to non-Hispanic patients was 20.7 (SD=6.5) vs. 16.9 (SD=2.7), p=.001. A total of 157 infusions of PEG was administered to 74 patients. The average dose of PEG was 2780 IU with an average time of infusion of 128 minutes in those without HSR. The incidence of HSR for Hispanic patients was 31% compared to 18.8% for non-Hispanics, although this was non-significant (p=0.234). In 19 patients who experienced HSR, 84% were Grade 3 and one was a Grade 4. Most HSR occurred during consolidation (79.9%). Silent inactivation occurred in 3 patients (4%) and one patient experienced delayed clearance. The average asparaginase activity level at 7-10 and 14-17 days was 1.03 IU/mL (SD=0.35) and 0.71 IU/mL (SD=0.30), respectively. There was no significance in asparaginase activity levels between Hispanics and non-Hispanics (p>.05). Overall, 81% of all patients achieved a (-) minimal residual disease (MRD) at the end of induction with no difference in Hispanic (83.3%) versus non-Hispanics (78.1%). In an adjusted analysis to evaluate potential determinants of HSR, we noted that NCI HR at diagnosis (p=0.019) was associated with increased incidence of HSR, while obesity, sex and ethnicity were not (Table 2). Interestingly, age >8 years was associated with higher odds of HSR unadjusted for NCI HR (OR=3.83, p=.016). Conclusion: We found that the two factors which increase the odds of HSR are age > 8 years and NCI high risk at diagnosis. We will be able to confirm the efficacy of premedication with a larger cohort upon the completion of all patients enrolled. Both silent inactivation and delayed clearance was infrequent. Although the standard therapeutic asparaginase activity is widely accepted to be ≥ 0.1 IU/mL, we observed supratherapeutic levels at 1 and 2 weeks post PEG at 1.03 IU/mL and 0.71, respectively. We are currently performing additional analysis to evaluate PEG related toxicity in various ethnic groups, determining the single nucleotide polymorphisms (SNPs) involved in HSR and toxicity, and creating a dose model based on pharmacokinetic analysis. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Blinatumomab As Toxicity Sparing First Line Treatment of Children and Young Persons with B-Precursor Acute Lymphoblastic Leukaemia (B-ALL)

Introduction Recent studies have demonstrated that Blinatumomab is more effective and less toxic than intensive chemotherapy in children and young persons (CYP) with relapsed B-ALL. Although Blinatumomab is standard of care in adults with persistent MRD during first line therapy based on the BLAST study, there is no published evidence in CYP of its efficacy and toxicity in this setting. We report our experience of Blinatumomab as a toxicity sparing alternative to chemotherapy in first line treatment of CYP with B-ALL. Patients and Methods We audited the outcome of patients treated according to a consensus UK guideline for first line treatment with Blinatumomab of CYP patients with B-ALL who were considered unfit for post-remission intensive chemotherapy or CR1 HSCT because of toxicity to previous chemotherapy or significant co-morbidities. Treating clinicians obtained consent for treatment with Blinatumomab as standard of care after counselling patients and carers about the risk and benefits of this approach. The guideline mandated discussion of all such patients at national tumour board meetings and data was captured through a referral proforma and follow-up questionnaire. It recommended replacing consolidation and/or interim maintenance phases with 2 cycles of blinatumomab as a single agent with a 1-2 week break between cycles. Patients who obtained an MRD response (defined as MRD <0.01%) received delayed intensification (DI) followed by maintenance, or maintenance therapy alone if they were unfit for DI. Patients who had persistent MRD >0.01% were categorised as Blinatumomab failures and received either further chemotherapy, HSCT or CART depending on performance status. Events were defined as death, relapse, or secondary cancer. Results Sixty patients were eligible for analysis, including 4 cases of Ph+ ALL and 8 with Down syndrome. Compared to the B-ALL cohort in a previous trial, UKALL 2003, there was a higher proportion of NCI high risk, cytogenetic high risk, end of induction MRD positive and Down Syndrome patients (Table 1). All patients were in morphological complete remission prior to receiving Blinatumomab. Blinatumomab was administered for toxicity (47/60 (78%), including G3/4 pancreatitis, typhlitis, severe infections often requiring intensive care or surgery, disseminated fungal infections, CNS haemorrhage or liver failure) or co-morbidities (Down syndrome, Li-Fraumeni syndrome (n=2), Schimke immune-osseous dysplasia and 7q11.21-23 duplication) or in one case to minimise transfusion requirements (Jehovah's witness.) In the remaining 13 cases, blinatumomab was either administered for end of consolidation MRD of ≥0.05% (n=10) in patients unfit for intensive chemotherapy/HSCT, or positive end of induction MRD in patients with HR cytogenetics (n=3). Blinatumomab replaced consolidation and interim maintenance therapy in 32/60 (53%) cases, and interim maintenance in the remaining 28/60 (47%) cases. Blinatumomab was well tolerated with 1 G3 neurotoxicity (seizure in a Down syndrome patient who had not received prophylactic anti-convulsants) and no grade 2-4 CRS. Of the 50/60 patients with positive MRD pre-Blinatumomab (median = 0.1%, range = 0.01%-8%), 48 (96%) had a reduction in level to <0.01% (45 after cycle 1, 3 after cycle 2), and 10 patients maintained MRD negativity before and after 2 cycles of Blinatumomab. In the two patients who did not respond (3%), 1 received CART followed by transplant for persistent MRD, the other is receiving intensive chemotherapy. Of the responders, 47 (80%) received DI and maintenance and 10 maintenance alone. With a median follow up of 16 months (range 2-44 months), 2 patients have relapsed (1 at 2 years, the other at 9 months) but remain alive. The 4 patients with Ph+ ALL and the 8 with Down syndrome are alive and in remission, with a median follow up of 12.5 months (range 7-22 months). Conclusion In this large case series, we found Blinatumomab is safe and highly active with promising short-term efficacy in a higher risk cohort of CYP patients with B-ALL in first remission. Our results support its use in place of intensive chemotherapy for patients with relative chemo-intolerance. Furthermore, if the efficacy is sustained on longer follow-up, the results argue for replacing parts of post-remission intensive chemotherapy with Blinatumomab to reduce attendant morbidity and mortality. SS and AV are joint senior authors, AH and AM joint first authorsFigure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Blinatumomab Associated Seizure Risk in Patients with Down Syndrome and B-Lymphoblastic Leukemia: An Interim Report from Children's Oncology Group (COG) Study AALL1731

INTRODUCTIONChildren with Down Syndrome (DS) and B-lymphoblastic leukemia (B-ALL) are at an increased risk of both relapse and treatment-related mortality, compared to those without DS. On COG study AALL1731 for de novo B-ALL, patients with DS and higher risk features (DS-High) are non-randomly treated with a regimen replacing intensive elements of conventional chemotherapy with three 28-day cycles of blinatumomab, with the combined goals of reducing toxicity and enhancing anti-leukemic efficacy. The DS-High group includes all NCI high risk (HR) patients; NCI standard risk (SR) patients with end-induction minimal residual disease positivity (>0.01%), unfavorable cytogenetics, CNS3 status, steroid pre-treatment, neutral cytogenetics with CNS2 status, or testicular disease. Neurotoxicity is a known risk of blinatumomab, with an incidence of 4% in block 1 and 1% in block 2 among pediatric patients with relapsed ALL (Brown et al, JAMA 2021). However, the specific risk in patients with DS has not been described to date. Here, we provide an early report of increased seizure incidence associated with blinatumomab in older DS-High patients enrolled on AALL1731 to date.METHODSWe reviewed seizure incidence among patients with DS enrolled on AALL1731 from June 2019 to June 2021 who had proceeded to receive blinatumomab. Blinatumomab was administered at a dose of 15 mcg/m 2/day, using dexamethasone pre-medication in cycle 1. Infusions were interrupted for seizures, with resumption at 5 mcg/m 2/d permitted following full resolution for grade 1-3 seizures.RESULTSAmong DS NCI HR patients, 8 of 47 (17%) had a seizure during blinatumomab infusion (Table 1). All 8 seizures occurred in patients over 10 years old. Six of the 8 seizures occurred in the first cycle of blinatumomab, most in the first 3 days of the infusion. Four had concomitant fever or cytokine release syndrome. Seizures were grade 2 (n=2) or grade 3 (n=6), and all resolved with full neurologic recovery. Of the 8 patients, 5 elected to resume blinatumomab; no further seizures occurred in these patients. There was no indication of increased seizure risk among NCI SR DS-High patients (1 seizure among 11 patients), or among DS or non-DS patients receiving blinatumomab on other study strata (0 of 7 DS SR-Avg; 1 of 146 non-DS SR-Avg; and 2 of 120 non-DS SR-High).CONCLUSIONSThe incidence of seizures associated with blinatumomab in DS-ALL patients older than 10 years appears higher than previously reported in children without DS. The majority of seizures occurred within the first 3 days, all fully resolved with no sequelae, and no patient who resumed blinatumomab infusion at a lower rate experienced further seizures. Seizure prophylaxis may be advisable in DS patients while receiving blinatumomab, particularly those >10 years of age. Further follow-up and a larger sample size are needed to confirm incidence and identify risk factors predisposing DS patients to neurologic toxicity. [Display omitted] DisclosuresLi: Novartis Canada: Membership on an entity's Board of Directors or advisory committees. Raetz: Pfizer: Research Funding; Celgene: Other: DSMB member. Loh: MediSix therapeutics: Membership on an entity's Board of Directors or advisory committees. Gupta: Jazz Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees. Rau: Jazz Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Advisory Board; AbbVie Pharmaceuticals: Other: Spouse is employee and stock holder; Servier Pharmaceuticals: Consultancy. OffLabel Disclosure:This trial includes the use of blinatumomab in combination with chemotherapy for treatment of de novo B-lymphoblastic leukemia.

Severe Sepsis As Immune Stimulation and Protection from Relapse of Childhood Acute Lymphoblastic Leukemia (ALL): Results from a Pilot Study and Validation of Events in a National Administrative Dataset

Relapse remains the major clinical risk in children with ALL, and those with persistent minimal residual disease (MRD) after chemotherapy pose a particular therapeutic challenge given their chemoresistant cell population. We previously showed TLR agonists, an immune-stimulating drug class, generate durable memory immune responses against ALL cells in preclinical MRD models (Blood 2009; 114:2459). These drugs mimic the “danger” signal provided by severe sepsis/septic shock (SS) and may offer immunotherapeutic options for patients who fail or are not eligible for targeted immunotherapies. Demonstrating a protective effect of SS against ALL relapse would further support clinical development of TLR agonists. We hypothesize SS but not SIRS/sepsis (SIRS) will be associated with a decreased risk of ALL relapse, and this effect will be most pronounced in children with NCI high-risk (NCI-HR) disease who are more likely to have both SS exposures and relapses.We assembled and validated a cohort of over 13,000 children with newly diagnosed ALL using the Pediatric Health Information System (PHIS) database. SS exposures after start of induction chemotherapy were defined using ICD9 (NEJM 2003; 348:1546) and billing codes for blood cultures and resources indicating organ failures. ICD9 and pharmaceutical/procedure billing codes were also used to identify ALL relapses and blood/marrow transplantations (BMT). To determine the operating characteristics of these definitions of SS, relapse and BMT, we established a cohort of children from the Children's Hospital of Philadelphia (CHOP) including all patients diagnosed with ALL at CHOP from January 1, 2004 - December 31, 2013. Patients initially treated elsewhere or who left CHOP prior to the end of induction were excluded. Exposures and outcomes identified by manual chart review were considered the gold standard. Exposures were classified as SS or SIRS per the 2005 International Pediatric Sepsis Consensus Guidelines (Ped Crit Care Med 2005; 6:2) and documented until the first event or 3 years from diagnosis. Relapses and deaths were captured until 5 years from diagnosis. Patients were censored at BMT in first remission. We analyzed the data in this single-institution cohort as a pilot study to determine whether the effect of SS on relapse is in the direction we hypothesize. Demographics were evaluated using one-way ANOVA and chi-square. Cox regressions with time-dependent exposures were used to estimate hazard ratios (HR) for relapse by exposure: SS versus no SS, and any sepsis (SIRS + SS) versus none. We also present validation results for the identification of relapses and BMT in the PHIS cohort.Among 395 eligible CHOP patients with newly diagnosed ALL, there were 1736 total exposures (SIRS n=1696 and SS n=40). Demographics are presented in Table 1. SS occurred in 35 patients, SIRS was the maximum exposure in 318, and no sepsis was observed in 42. Exposure was associated with age and phenotype/NCI risk status. Median follow-up was 1826 days (IQR 28-1826), and median time to first SS 117 days (IQR 53-356). There were 521 organisms documented during sepsis episodes (Table 2). BMT in CR1 was the first event in 22 patients (5.6%) at median 174 days from diagnosis (IQR 143-240), relapse in 47 (11.9%; 580 days, 260-1106), and remission death in 5 (1.3%; median 252 days, 98-348). Unadjusted analysis showed a detrimental effect of SS on relapse (HR 2.45; 95%CI 1.04, 5.79). Adjusting for NCI-HR decreased the SS effect size (HR 1.74; 0.7, 4.29), and limiting to NCI-HR patients shifted the effect into a protective direction (crude HR 0.71; 0.09, 5.43). Any sepsis was not protective in any analysis (crude HR 1.86; 0.66, 5.25; adjusted HR 1.71; 0.61, 4.81; NCI-HR-only HR 2.47; 0.32, 19.1). Our relapse identification method within the national PHIS cohort had sensitivity 76% and positive predictive value (PPV) 91%, while BMT identification sensitivity was 93% and PPV 100%.Our CHOP pilot study demonstrated a detrimental effect of SS on the cohort as a whole, suggesting most children with ALL incur more risk than benefit from SS exposure; however, the hazard ratio for SS is in the direction of protection in the NCI-HR group. We have validated our approach to identifying relapse and BMT in PHIS and are validating our method to detect SS exposures in PHIS. Evaluation of the association between SS and relapse risk in the larger, multi-institutional PHIS cohort will provide more precise effect estimates. [Display omitted] DisclosuresFisher:Merck: Research Funding; Pfizer: Research Funding.

Genomic and Outcome Analyses of Philadelphia Chromosome-like (Ph-like) NCI Standard Risk B-Acute Lymphoblastic Leukemia (SR B-ALL) Patients Treated on Children's Oncology Group (COG) AALL0331

Introduction: Ph-like ALL is defined by a gene expression profile similar to Philadelphia chromosome-positive ALL but lacking the BCR - ABL1 fusion. Ph-like ALL is comprised of diverse genomic alterations activating kinase and cytokine receptor signaling, including chimeric fusions involving ABL1 and related genes (ABL2, CSF1R, PDGFRB ; ABL-class fusions), genomic rearrangements leading to CRLF2 over-expression, JAK2 gene fusions, and truncating rearrangements of EPOR . We have published several large studies describing the clinical features, treatment outcome, and genomic alterations in Ph-like ALL that focused on patients with NCI high risk (HR) ALL (age ≥10 years or WBC ≥50,000) or those with SR ALL (age 1-9.99 years and WBC <50,000) and elevated minimal residual disease (MRD) at the end of induction (EOI; Reshmi, BLOOD 2017 and Roberts, NEJM 2014). The purpose of the current study was to assess the frequency of genomic lesions in Ph-like SR ALL patients lacking HR features.Methods: We retrospectively analyzed 1023 unselected newly-diagnosed SR ALL patients enrolled on COG AALL0331 between 2006 and 2008, and compared characteristics of SR Ph-like cases to the HR patients described in our prior studies. All cases were screened using an 8-gene Taqman low-density array (LDA) PCR assay to identify the Ph-like GEP (Harvey, ASH 2013). Ph-like cases with elevated CRLF2 expression were tested for CRLF2 rearrangement (CRLF2 -R; P2RY8 - CRLF2 by Taqman PCR on the LDA card and IGH - CRLF2 by FISH). JAK mutations in CRLF2 -R cases were tested by Sanger sequencing. Ph-like cases without CRLF2 -R were tested for previously identified kinase fusions involving ABL1, ABL2, CSF1R, JAK2, NTRK3, and PDGFRB by RT-PCR. A subset of Ph-like cases without detected genomic alterations underwent RNA-sequencing using standard Illumina library preparation.Results: A total of 205 patients had LDA value ≥0.5, with 145 (14.2%) remaining after exclusion of BCR-ABL1 and ETV6-RUNX1 . Of these 145, 85 were CRLF2high (57.9%) as defined by CRLF2 expression levels on the LDA card. Among these 85, 42 (50%) had CRLF2 -R, compared to 80% in HR patients. P2RY8 - CRLF2 was seen in 36 cases, IGH - CRLF2 in 4 and 2 had CRLF2 -R with an unknown partner; 14 (32.6%) of these had a concomitant JAK mutation. Of the 60 Ph-like CRLF2low cases, five had a targetable kinase fusion identified by RT-PCR or RNA sequencing: two ABL - class fusions (ZMIZ1 - ABL1, EBF1-PDGFRB); one PAX5-JAK2 fusion; one ETV6-JAK2 fusion; and one ETV6 - NTRK3 fusion. The 145 Ph-like cases had inferior 7-year event-free survival (EFS; 83.1±3.5% vs. 90.6 ±0.1%; P=0.005) and non-significantly inferior 7-year overall survival (OS; 93.5±2.3% vs. 95.5 ±0.8%; P=0.184) compared to 869 non Ph-like cases. Ph-like ALL cases were more likely to have end induction MRD ≥ 0.01% (24.3% vs. 17.9%; P=0.049), and positive MRD was predictive of outcome for Ph-like (7-year EFS: 73.2±8.3%, vs. 86.6 ±3.7%; P=0.079; 7-year OS: 88.2 ±5.9% vs. 95.9±2.1%; P=0.162) and non Ph-like patients (7-year EFS: 79.7 ±3.7% vs. 93.3 ±1.0%; P <0.0001; 7-year OS: 90.2% SE 2.7 vs. 97.4±0.9%; P <0.0001). In multivariate analyses, Ph-like and MRD status EOI were significant predictors of EFS (p=0.016; <0.0001 respectively), while only MRD had a significant impact on OS.Conclusion: Ph-like ALL is less common in NCI SR than HR patients with significant differences in the frequency of various genomic alterations in Ph-like ALL cases based on NCI risk group. Our previous studies have shown that Ph-like ALL HR patients have a substantially increased risk of treatment failure and death as compared to non Ph-like HR patients (Mullighan, NEJM 2009 and Roberts, NEJM 2014). This cohort of SR Ph-like patients had a significantly inferior EFS and a trend to inferior OS, but the magnitude of effect was much smaller than that seen in HR Ph-like patients, with overall outcomes much better in SR as compared to HR Ph-like patients. These findings underscore the significant differences in Ph-like ALL frequency, genetic subtypes, and outcome based on age and initial WBC. [Display omitted] DisclosuresBorowitz:Beckman Coulter: Honoraria; Becton-Dickinson Biosciences: Research Funding; HTG Molecular: Honoraria. Zweidler-McKay:ImmunoGen: Employment. Mattano:HARP Pharma Consulting, LLC: Employment. Mullighan:Loxo Oncology: Research Funding; Amgen: Consultancy. Hunger:Amgen: Consultancy, Equity Ownership; Novartis: Consultancy; Erytech Pharmaceuticals: Consultancy; Jazz Pharmaceuticals: Honoraria.

Fertility Status Among Long-Term Childhood Acute Lymphoblastic Leukemia Survivors Enrolled between 1971 and 1998 in the EORTC Children Leukemia Group Trials 58741, 58831/2 and 58881

BackgroundThe survival of childhood acute lymphoblastic leukemia (ALL) has improved significantly over the last decades, with recently reported overall survival rates in Europe of up to 85% in children (<14 years) and 62% in adolescents (15-19 years) (Trama, Lancet Oncol 2016). The increased number of long-term survivors has made the management of side effects an increasingly important issue in pediatric oncology. In this context, the impact on fertility caused by widely employed ALL treatments such as alkylating agents, cranial radiotherapy, total body irradiation and orchiectomy has been an emerging concern over the last years. The aim of this study was to assess fertility among long-term childhood ALL survivors.MethodsBetween 2012 and 2017, a follow-up study was performed among childhood ALL (and acute lymphoblastic lymphoma) survivors enrolled between 1971 and 1998 in EORTC studies (58741, 58831/2, 58881) in France and Belgium. Patients <18 years (yrs) at diagnosis and ≥18 yrs at the time of the follow-up were eligible to fill out a questionnaire that included information about their fertility. The following fertility-related outcomes were evaluated: having menstrual cycles for females, intention to have children, having children, use of reproductive techniques to become pregnant and occurrence of negative pregnancy outcomes (miscarriage, medical abortion, birth defects), separately for males and females.ResultsOut of 1429 eligible patients, 502 (35%) filled out the questionnaire, 862 (60%) were lost to follow-up, and 65 (5%) refused to participate. Disease characteristics and relapse occurrence within one yr after diagnosis were comparable between these 3 groups.Among respondents (275 females, 227 males), approximately 14% were aged 10-17 yrs at diagnosis and almost 30% belonged to the NCI high risk group (Table 1). Approximately 12% received cranial radiotherapy and 6% of females and 8% of males underwent hematopoietic stem cell transplantation. Relapse occurred in 12% and 14% of females and males, respectively. The median time between the diagnosis and the socioeconomic evaluation was 20 yrs (range: 13-42). The median age at follow-up was 25 yrs (range: 18-53).All but 6 females had ever had menstrual cycles. At the time of the fertility evaluation, 93% out of females younger than 45 yrs of age (N=270) either had menstrual cycles, were pregnant, gave breast feeding or continuously used contraceptives. Among females who had tried to become pregnant, 89% had been pregnant, 75% had children and 12% used medical help to become pregnant. One fifth of the ever pregnant females had ever had a miscarriage. The incidences of other negative pregnancy outcomes (e.g. birth defect, medical abortion) were low.The average number of children females had was 0.36 (95% CI: 0.27-0.44). The expected number of children in a population with the same distribution of country, age, and yr of birth of the mothers based on national population registries was 0.55. However, as 52% of the females had a bachelor or master degree and only 3% had no secondary school diploma, this difference could possibly be explained by an overrepresentation of females with a high level of education in our sample.Among males who had tried to have children, 83% made their partner pregnant, 72% had children and 7% used medical help to make their partner pregnant. The incidence of negative pregnancy outcomes other than miscarriage was low.ConclusionsIn this first disease-specific European cohort study, we evaluated fertility among adult survivors of childhood ALL enrolled in EORTC trials, with a median time from the diagnosis of 20 yrs.Most survivors who tried to have children, succeeded (75% of females, 72% of males). However, the average number of children per female seemed to be lower than in the general population. The incidences of birth defects, and medical abortions were low, both among female survivors and the partners of the male survivors.Despite the large number of potentially eligible patients, we could evaluate only 35% of long-term survivors. We were unable to study the effect of specific treatment exposures due to the large variety of treatments that patients received, the association between some treatments (protocol dependent) and age at the fertility evaluation, and the need to stratify the analyses by sex. Improvements in the follow-up of childhood cancer survivors are needed for a better evaluation of the long-term outcomes. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Minimal residual disease at end of induction and consolidation remain important prognostic indicators for newly diagnosed children and young adults with very high-risk (VHR) B-lymphoblastic leukemia (B-ALL): Children’s Oncology Group AALL1131.

10004 Background: Children and young adults with very high risk (VHR) B-acute lymphoblastic leukemia (B-ALL) [13-30 years of age with any features or 1-30 years of age with adverse prognostic features including KMT2A rearrangements, iAMP21, hypodiploidy (&lt;44 chromosomes/DNA index &lt; 0.81), central nervous system disease, end of induction (EOI) minimal residual disease (MRD) &gt;0.01%, or induction failure] collectively have a predicted 4-year disease free survival (DFS) of approximately 70%. Whether patients with VHR B-ALL who are MRD positive at EOI and become MRD negative at the end of consolidation (EOC) will have improved survival versus patients remaining MRD positive at EOC is unknown. Methods: Patients with newly diagnosed NCI high risk B-ALL enrolled on AALL1131 or NCI standard risk B-ALL enrolled on AALL0932 and classified as VHR at EOI were treated on the VHR stratum of AALL1131 which sought to improve DFS with intensive post-Induction therapy using fractionated cyclophosphamide (CPM), etoposide (ETOP) and clofarabine (CLOF).Patients were randomly assigned post-Induction to Control Arm (CA) with modified augmented BFM CPM + fractionated cytarabine + mercaptopurine, Experimental Arm 1 (Exp1) with CPM + ETOP, or Experimental Arm 2 (Exp2) with CLOF + CPM + ETOP during Part 2 of Consolidation and Delayed Intensification. Doses of vincristine and pegaspargase were identical on all arms. Exp2 was permanently closed September 2014 due to excessive toxicities, and these patients are excluded from this report. MRD was measured by 6-color flow cytometry at EOI and for those who consented at the EOC. Results: 4-yr DFS for all patients (n=823) with VHR B-ALL was 76.8 ± 2.0%. As we reported previously, 4-year DFS was not significantly different between CA and Exp 1 (85.5 ± 6.8% versus 72.3 ± 6.3%; p=0.76; Burke, Haematologica 2019). 4-yr DFS for patients who were EOI MRD &lt;0.01%, (n=325) versus &gt;0.01 (n=498) was 83.3% ± 2.6% vs 72.0% ± 2.8%, p=0.0013. 4-Year DFS of Patients EOI MRD &gt; 0.01%. Conclusions: MRD is a powerful prognostic indicator in VHR B-ALL with inferior outcomes in patients who are EOI MRD positive. Among patients who were EOI MRD positive treated on Exp1, outcomes were similar for EOC MRD negative and EOC MRD positive, though numbers were small. In contrast, patients who were EOI MRD positive treated on CA that were EOC MRD negative had significantly improved DFS compared to those that were EOC MRD positive. The CA remains the standard of care for COG ALL trials. With this therapy, patients with VHR B-ALL that are EOI MRD positive and EOC MRD negative have significantly improved DFS compared to those that remain MRD positive at EOC. Clinical trial information: NCT02883049. [Table: see text]

Response Adapted Therapy in ETV6/RUNX1-Positive Childhood Acute Lymphoblastic Leukemia Treated per Modified St Jude Total XV Study

Introduction: ETV6-RUNX1 is the most common genetic aberration in childhood acute lymphoblastic leukemia (ALL), occurring in approximately 25% of cases with a precursor-B phenotype. The presence of ETV6-RUNX1 has been associated with a relatively low rate of relapse in multiple studies. Relapses tend to occur late and have a better salvage rate than other ALL subtypes. Moreover, conflicting data in literature regarding the prognostic significance of ETV6-RUNX1 after accounting for age, initial count and treatment intensity. We sought to study the clinical features, therapy response in newly diagnosed ETV6-RUNX1-positive treated at King Hussein Cancer Center. Methods: Patients were treated per modified St Jude Total (XV) study, risk stratification was further refined by including minimal residual disease (MRD)measurements on day 15 and day 46 of remission induction therapy. Patients with the ETV6- RUNX1 fusion or hyperdiploidy without CNS or testicular disease and a satisfactory early MRD decline (&amp;lt;1% on day 15 and &amp;lt;0.01% on day 46) were classified as being low-risk for relapse and were treated on lower -risk arm regardless of age and leukocyte count. Results: Seventy patients (n=70) with ETV6-RUNX1-positive treated at our institution between May 2006 to October 2017. The median age at diagnosis, 5.8 years (range, 1.5-10.8). ETV6-RUNX1 was associated with favorable age between 1- and 6-years in 55 patients (79%), male gender in 41 patients (59%), initial leukocyte count &amp;lt;10 in 39 patients (56%), CNS status 1 in 100% of patients. The majority, n= 58 (83%) of patients had NCI standard risk (SR) and n=12 (17%) had NCI high risk (HR). Sixty-six patients (94%) had MRD &amp;lt;1% at day 15 and all patients achieved remission with MRD&amp;lt;0.01% at day 46 of remission induction. All patients were treated as LR ALL per modified St Jude total XV protocol. At median follow up of (36 months; range, 26 to 154), in the subgroups of ETV6-RUNX1-positive patients classified as NCI standard risk (SR)and NCI high risk (HR) the 5-year EFS estimates were 94.1% ± 3.2 and 82%±1(P=.13), 5-year OS estimates were 100% and 92% ± 8 (p=0.31) respectively. Conclusion: MRD treatment schema in ETV6/RUNX1 -positive patients have excellent outcomes if they achieved favorable response at day 15 and end of remission induction regardless of the age and Initial leukocyte count. Treatment reduction is feasible and declared safe for children with NCI-HR who are predicted to have a low risk of relapse on the basis of rapid clearance of MRD post remission induction therapy. Disclosures No relevant conflicts of interest to declare.

Impact of Asparaginase Discontinuation on Outcome in Childhood Acute Lymphoblastic Leukemia: A Report From the Children's Oncology Group.

Asparaginase (ASNase) is an important component of acute lymphoblastic leukemia (ALL) treatment, but is often discontinued because of toxicity. Erwinia chrysanthemi ASNase (Erwinia) substitution was approved in 2011 for allergic reactions. Erwinia has, however, been intermittently unavailable because of drug supply issues. The impact of Erwinia substitution or complete ASNase discontinuation is unknown. Patients aged 1-30.99 years in frontline Children's Oncology Group trials for B-cell acute lymphoblastic leukemia between 2004 and 2011 (National Cancer Institute [NCI] standard risk [SR]: AALL0331; NCI high risk: AALL0232) were included. The number of prescribed pegaspargase (PEG-ASNase) doses varied by trial and strata. Maintenance therapy did not contain ASNase. Landmark analyses at maintenance compared disease-free survival (DFS) among those receiving all prescribed PEG-ASNase doses versus switching to Erwinia but receiving all doses versus not receiving all ASNase doses. We included 5,195 AALL0331 and 3,001 AALL0232 patients. The cumulative incidence of PEG-ASNase discontinuation was 12.2% ± 4.6% in AALL0331 and 25.4% ± 0.8% in AALL0232. In multivariable analyses, NCI high-risk patients not receiving all prescribed ASNase doses had inferior DFS (hazard ratio [HR], 1.5; 95% CI, 1.2 to 1.9; P = .002) compared with those receiving all prescribed PEG-ASNase doses. Patients with Erwinia substitution who completed subsequent courses were not at increased risk (HR, 1.1; 95% CI, 0.7 to 1.6; P = .69). NCI SR patients who discontinued ASNase were not at elevated risk (HR, 1.2; 95% CI, 0.9 to 1.6; P = .23), except when restricted to those with slow early response, who were prescribed more ASNase because of therapy intensification (HR, 1.7; 95% CI, 1.1 to 2.7; P = .03). Discontinuation of ASNase doses is associated with inferior DFS in higher-risk patients. Our results illustrate the severe consequences of Erwinia shortages.

PI3Kδ Inhibition Enhances Sensitivity of Primary High-Risk Childhood B-Cell Acute Lymphoblastic Leukemia Cells to Glucocorticoid Chemotherapy

Introduction: Despite excellent 5-year survival for most patients with B-cell acute lymphoblastic leukemia (B-ALL), those with high-risk (HR) B-ALL continue to have inferior outcomes. The prognosis is even worse for patients who respond poorly to chemotherapy, and improvements to current therapy approaches are needed. Glucocorticoids (GCs) are a key component of chemotherapy regimens. Rapid response to GC monotherapy is a well-documented predictor of favorable outcomes, while slow response to GCs correlates with poor outcomes. We hypothesized that enhancing specific GC toxicity to B-ALL cells can improve clinical outcomes for high-risk patients without increasing systemic toxicity. PI3Kδ is a promising target for this purpose. PI3Kδ is a critical component of the B-cell receptor cell-survival pathway; it restrains GC signaling, while GCs repress its expression. PI3Kδ expression is restricted to lymphoid cells, making it an appealing precision target to enhance GC toxicity in lymphoid cells while minimizing risk of increased systemic GC-associated toxicity. We previously demonstrated synergy between dexamethasone (dex) and the FDA-approved isoform-selective PI3Kδ inhibitor idelalisib (idela) in B-ALL cell lines, patient specimens, and patient-derived xenograft models (Kruth et al Blood 2017). In clinical practice, both dex and prednisone (pred) are essential components of childhood ALL chemotherapy. In this study, we sought to elucidate the extent to which idela in combination with dex or pred could induce synergistic killing of HR B-ALL specimens with various genetic backgrounds. Methods: Peripheral blood or bone marrow from patients ages 1-31 years with newly-diagnosed NCI HR or standard-risk (SR) B-ALL at the University of Iowa Stead Family Children's Hospital was obtained after informed consent on an Institutional Review Board-approved research study. Mononuclear cells were isolated from the specimens via Ficoll gradients and cultured in vitro in 384-well plates. Immediately after isolation, cells were treated with serial dilutions of the GCs dex or pred and idela in RPMI1640+10% FBS medium. Cell viability was measured with PrestoBlue (Invitrogen) after 72 hours of treatment. Survival curves were plotted to determine the LD50 of each drug using GraphPad. Dose effects around the LD50 for each drug were analyzed using Compusyn to determine if the drug combination was synergistic (combination index, CI &lt;1), additive (CI=1), or antagonistic (CI &gt;1). Results: As of August 1, 2019, 5 HR B-ALL patient specimens of various genetic alterations have been tested. Two patients were high-risk at diagnosis due to steroid pre-treatment (MAP011) or by NCI risk criteria (age &gt;10 years and/or WBC count &gt;50K/mm3; MAP014). Three patients with initially SR B-ALL were upstaged due to minimal residual disease (MRD) &gt;1% at day 8 in peripheral blood (MAP012) or marrow MRD ≥0.01% at end of induction (MAP009, MAP010). In our in vitro studies, only one sample (MAP014) showed reduced viability with GC alone, while 4 specimens (all except MAP012) responded to idela alone. Most specimens showed a synergistic response to dex or pred in combination with idela with greater reduction in cell viability compared to GC monotherapies. Surprisingly, one specimen (MAP010) had an antagonistic response with pred and idela combination. This near-haploid B-ALL specimen had reduced viability with idela monotherapy, but an antagonistic response with single-agent pred, raising the question of whether GC/idela synergy is influenced by genetic background. Conclusions: In pilot studies, idela sensitized HR B-ALL cells to GC chemotherapy and is a promising strategy for further evaluation in a larger cohort of specimens. Our results highlight the potential impact of genetic heterogeneity within childhood B-ALL upon differential therapeutic responses to standard steroid chemotherapy and demonstrate a potential precision medicine approach to augment GC sensitivity via combination with selective PI3Kδ inhibition. Disclosures Tasian: Gilead Sciences: Research Funding; Aleta Biotherapeutics: Membership on an entity's Board of Directors or advisory committees; Incyte Corportation: Research Funding.

Plasma asparaginase activity and asparagine depletion in acute lymphoblastic leukemia patients treated with pegaspargase on Children’s Oncology Group AALL07P4

The efficacy of asparaginase in acute lymphoblastic leukemia (ALL) is dependent on depletion of asparagine, an essential amino acid for ALL cells. The target level of plasma asparaginase activity to achieve asparagine depletion has been between 0.05 and 0.4 IU/mL. COG AALL07P4 examined the asparaginase activity and plasma and CSF asparagine concentration of pegaspargase when given intravenously in the treatment of NCI high risk ALL. Matched plasma asparaginase/asparagine levels of the clearance of 54 doses of pegaspargase given in induction or consolidation demonstrated that all patients who had a plasma asparaginase level >0.02 IU/mL had undetectable plasma asparagine. No difference was observed in CSF asparagine levels associated with matched plasma asparaginase levels of 0.02–0.049 versus 0.05–0.22 IU/mL (p = .25). Our data suggest that a plasma asparaginase activity level of 0.02 IU/mL can effectively deplete plasma asparagine. The data also indicate that the 95% CI for plasma asparagine depletion after a pegaspargase dose is 22–29 days.Clinical trial registration: clinicaltrials.gov identifier NCT00671034.

Preliminary Outcomes of Children and Young Adults with Acute Lymphoblastic Leukaemia and Down Syndrome (DS-ALL) on UKALL 2011. Reduction in Treatment-Related Mortality with De-Escalated Therapy

IntroductionReported outcomes for children with Downs syndrome (DS) and acute lymphoblastic leukaemia (ALL) treated on our previous national study, UKALL 2003, were inferior compared to non-DS children. 5 year event free survival (EFS) for DS children was 65.6% vs. 87.7% for non-DS children and 5 year overall survival (OS) was 70.0% vs. 92.2% (British Journal of Haematology 2014; 165: 552-555). Excess treatment related mortality (TRM, 21.6% vs. 3.3% at 5 years) in children with DS-ALL was primarily due to infection. Similar results have been reported by other study groups.In our successor study, UKALL 2011, we employed several steps of de-escalation for DS-ALL patients compared to standard therapy. Here, we report that de-escalated therapy has resulted in a dramatic reduction in TRM for children with DS-ALL treated in the UK. MethodsDS-ALL patients treated on UKALL 2011 had their treatment modified in the following respects: 1)NCI high risk patients did not receive anthracycline in induction unless they had a slow early response at day 15; 2) two years maintenance was given for both boys and girls; 3) no pulses were given in maintenance for MRD low risk patients.In addition, we recommended use of prophylactic antibiotics during induction and intensive phases of treatment. Fisher's exact test was used to compare induction mortality in the DS and non-DS pts. OS was defined as time from registration to death. EFS was defined as time from registration to first event (induction failure, relapse, second malignancy or death from any cause). The Kaplan-Meier method was used for survival estimation. ResultsThe UKALL 2011 trial opened to recruitment on 26th April 2012 and has recruited 2362 patients, of whom 50 have Down syndrome, in the period up to 22nd February 2018. The study is open in 41 centres in UK and Ireland and included patients with both ALL and lymphoblastic lymphoma (LBL). The baseline characteristics of the patients recruited up to this date are shown in the table below. For DS-ALL, Day 29 MRD was available for 48 patients and was low risk in 25 cases (50%), risk in 19 (38 %) and no result was obtained in 4 (8 %). The therapy was generally well-tolerated, there have been no cases of therapy curtailment due to toxicity and only one patient due to receive intensified therapy per MRD risk assessment was unable to escalate due to toxicity.At a median follow-up of 32.7 months, there have been 4 events. These include two relapses (relapse rate: 4.1% (1.1-15.5) at 3 years) and two TRMs (one TRM in induction and the other in consolidation; both due to infection). Three year EFS is: 92.9% (95% CI: 79.1 - 97.7) with a three year OS of 95.9% (84.5 - 99.0). The remarkably low induction TRM for DS children on UKALL 2011 (1 death out of 50 patients, 2%), is comparable to that of non-DS children treated on the same protocol with a 3 drug induction (12 out of 1174 children, 1% induction TRM; induction TRM in DS-ALL vs non-DS-ALL p=0.42). It is also comparable to the induction TRM in DS-ALL noted in the latter half of the UKALL 2003 study (1/40, 2.5%) when the aforementioned treatment modifications were first implemented in the UK.Importantly, this TRM is a quarter of that when an historic cohort of DS-ALL children were treated with a 4-drug induction on our previous study (UKALL 2003, DS-ALL TRM 4/46 patients i.e. 8 %, p=0.19). ConclusionThese preliminary results suggest that de-escalation of treatment is successful in reducing treatment related mortality for children with DS-ALL without increasing the risk of early relapse, however longer term follow-up is needed. DisclosuresGhorashian:Celgene: Other: travel support; Novartis: Honoraria. Hough:University College London Hospital's NHS Foundation Trust: Employment. Kearns:Pfizer: Consultancy, Research Funding; Galen: Research Funding. Vora:Jazz: Other: Advisory board; Medac: Other: Advisory board; Pfizer: Other: Advisory board; Amgen: Other: Advisory board; Novartis: Other: Advisory board.

Whole Exome Sequencing of Pediatric Acute Lymphoblastic Leukemia Patients Identify Mutations in 11 Pathways: A Report from the Children's Oncology Group

Survival for childhood acute lymphoblastic leukemia (ALL) now approaches 90% with risk adapted therapy based on National Cancer Institute risk group (NCI RG) at diagnosis, somatic lymphoblast genetics, and early response to therapy as measured by minimal residual disease (MRD). Recent studies have identified multiple somatic genetic mutations in ALL, some of which confer increased risk of relapse or identify opportunities for additional targeted therapies. However, there are few genome sequencing analyses of representative cohorts of childhood ALL treated on contemporary regimens.To define the mutational landscape of childhood B-ALL, we performed whole exome sequencing (WES) on diagnostic tumor and remission samples of 192 patients with B-ALL consecutively enrolled between 4/1/06-9/8/06 on the Children’s Oncology Group AALL03B1 classification trial that enrolled 11,145 patients up to age 30, which included patients enrolled on clinical trials for standard-risk (SR) B-ALL (N=5226, age 1-10 years and white blood cell count (WBC) < 50,000/uL) and high-risk (HR) B-ALL (N=2907; age ≥10 years or WBC ≥50,000/uL). An 8-gene expression low density array card identified Ph-like patients, and single nucleotide polymorphism arrays and multiplex ligation assays were used to determine DNA copy number alterations. Approximately 2/3 NCI SR and 1/3 NCI HR patients with sufficient banked samples were selected to reflect a population-based cohort (Table 1). Comparison of those selected vs. those not revealed significantly more NCI SR patients with a higher WBC and MRD, and fewer with double trisomy 4 and 10. Selected NCI HR patients were younger, had a higher WBC, and had more ETV6/RUNX1.There were a total of 3576 non-silent mutations with a median of 15 mutations/case (range 1-134). One case had 102 non-silent mutations and a germline mutation in MSH3. The additional mutations clustered in 11 pathways (Table 2), several of which were novel including cell-matrix interaction (e.g. SSPO, FAT1) and intracellular trafficking/cytoplasmic transport (e.g. DYNC2H1, ANK3, UNC13C). Most commonly altered were B-cell development (49.4%), transcription factors (45.8%), tumor suppressor genes (32.7%), cytoplasmic transport (27.3%), and Ras signaling (26.7%). Several pathways Ras signaling, Jak/STAT, and transcription factor mutations/deletions were associated with genetic lesions commonly used for risk stratification. Other pathways (epigenetic, B-cell development, or tumor suppressor) occurred in all subtypes. The most commonly identified genetic mutations were NRAS (n=33), KRAS (n=26), FLT3 (n=13), PAX5 (n=10), CREBBP (n=10), XBP1 (n=9), WHSC1 (n=7), and UBA2 (n=7). XBP1 and UBA2 mutations were novel. XBP1 (X-Box binding Protein 1) encodes a transcription factor that regulates the unfolded protein response. UBA2 (ubiquitin like modifier activating enzyme 2) encodes a protein involved in sumoylation to regulate protein structure and intracellular localization. Univariable analysis revealed no significant associations with any of these pathways or mutations with an increased risk of relapse with the exception of IKZF1 mutations or deletions (n=36; p=0.0087). Multivariable analysis modeling including IKZF1, age, presenting WBC, gender, NCI RG, ETV6/RUNX1, BCR/ABL1, Ph-like, white race, and MRD revealed only BCR/ABL1 and MRD positivity being significantly predictive of relapse. However, the risk of relapse was significantly increased based on the number of mutations identified in any one single patient (HR 1.02, 95% CI 1.01-1.023, p < 0.0004). Of note, only 18 patients (NCI SR, n=8, NCI HR, n=10) were Ph-like in this cohort, likely explaining the lack of significance between Ph-like status and an increased risk of relapse in this analysis.In summary, WES of a consecutively enrolled cohort of NCI SR and HR patients revealed a large number of novel genetic mutations that could be broadly assigned to 11 classes. Outcomes for patients overall were not influenced by any one of these classes, demonstrating that sentinel genetic alterations currently used in risk stratification are of paramount importance in directing therapy intensification for ALL. These data provide important information about pathways commonly mutated in childhood ALL, identifying classes of drugs that can be considered for clinical testing to further improve outcome. [Display omitted] [Display omitted] DisclosuresLoh:Bristol Myers Squibb: Membership on an entity’s Board of Directors or advisory committees; Abbvie: Research Funding. Hunger:Amgen: Equity Ownership; Pfizer: Equity Ownership; Merck: Equity Ownership; Jazz Pharmaceuticals: Honoraria; Sigma Tau Pharmaceuticals: Honoraria; Erytech: Honoraria; Patent: Patents & Royalties: Dr. Hunger is a co-inventor of a patent (#8658,964) for the identification of novel subgroups in high risk B-ALL and outcome correlations and diagnostic methods related to the same; Spectrum Pharmaceuticals: Honoraria.

Kinase-Activating Fusions in Pediatric High-Risk B-Lineage Acute Lymphoblastic Leukemia (ALL): a Report from the Dana-Farber Cancer Institute (DFCI) ALL Consortium

Abstract Background. Recurrent chromosomal rearrangements carry prognostic significance in pediatric B-lineage acute lymphoblastic leukemia (B-ALL). Recent genome-wide analyses identified a diverse spectrum of chromosomal rearrangements resulting in novel chimeric fusions associated with poor prognosis when treated with conventional chemotherapy. These fusions are observed more frequently in NCI High-Risk (HR) B-ALL compared with NCI Standard Risk (SR) patients. They often activate ABL and JAK-STAT signaling pathways and have demonstrated sensitivity to the relevant tyrosine kinase inhibitors (TKIs) in in vitro assays and ex vivomodels. The objective of this study was to determine the frequency of NCI HR B-ALL patients enrolled on DFCI ALL Consortium Protocol 05-001 with a kinase-activating fusion that would be amenable to TKI therapy and to describe their associated clinical characteristics and outcomes. Methods. Between 2005-2011, 219 NCI HR, Philadelphia chromosome (Ph)-negative, B-ALL patients were enrolled on DFCI ALL Consortium Protocol 05-001, 105 of whom had sufficient material to undergo kinase fusion testing by validated multiplex reverse transcription polymerase chain reaction (RT-PCR) assays. A total of 35 kinase fusions of ABL-class (ABL1, ABL2, PDGFRB, CSF1R), JAK2 and CRLF2 rearrangements were examined. IGH@-CRLF2 and EPOR rearrangements were not assessed. Fusion products were predicted by NCBI BLAST algorithms, confirmed by singleplex PCR and Sanger sequencing and aligned using CLC Main Workbench Version 7.6.1. IKZF1 deletion (del) status had previously been assessed by multiplex ligation-dependent probe amplification (MLPA). Fisher's exact test and the Wilcoxon rank sum test were used to compare patient characteristics to those with and without any identified fusion for categorical and continuous variables respectively. Event-free survival (EFS) and overall survival (OS) were estimated with the Kaplan-Meier method and compared using a log rank test. Univariate and multivariable Cox proportional hazards models of EFS were constructed. Results. Among 105 NCI HR, Ph-negative, B-ALL patients, 16 (15%) were found to harbor an ABL-class fusion (ETV6-ABL1: n=1; FOXP1-ABL1: n=1; SFPQ-ABL1: n=1; ZC3HAV1-ABL2: n=1) or a fusion activating the JAK-STAT pathway (P2RY8-CRLF2: n=8; PAX5-JAK2: n=4). Sixty-nine percent of patients with an identified fusion (Fusion +) had a concomitant IKZF1 del (n=11). Features associated with fusion-positivity were age of 10 years or older (p=0.003), male sex (p=0.03), Hispanic ethnicity (p=0.01) and IKZF1 del (p=0.0005) (Table 1). Fifty percent of Fusion+ patients experienced an event (induction death (n=1); induction failure (n=1); or relapse (n=6)) compared to 24% of patients without a fusion. The 5-year EFS and OS were 48% (95% CI 22-70%) and 68% (95% CI 39-85%) for Fusion+ patients compared to 78% (95% CI 67-85%) and 88% (95% CI 79-93%) for those without fusions (Figure 1). In univariate analysis, fusion-positivity (HR: 2.66, p=0.02) and IKZF1 del (HR: 3.21; p=0.0018) were each significantly associated with inferior EFS, while age and presenting leukocyte count were not. In multivariable analysis, IKZF1 del, but not fusion-positivity, retained statistical significance (HR: 2.64, p=0.02). Conclusion. Fifteen percent of NCI HR, Ph-negative, B-ALL patients enrolled on DFCI ALL Consortium 05-001 were found to have a kinase-activating fusion. Fusion+ patients frequently harbored concomitant IKZF1 deletion and had an inferior outcome. Future studies should focus on developing clinical strategies to rapidly identify these patients at diagnosis and to test whether the addition of the relevant TKIs to their treatment will improve their outcome. Disclosures Asselin: Jazz Pharmaceuticals: Consultancy, Speakers Bureau; Sigma Tau Pharamceuticals: Consultancy. Loh:Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees; Abbvie: Research Funding.

Investigating Ethnic Differences in Toxicities of Childhood ALL Therapy

IntroductionAcute lymphoblastic leukemia (ALL) is the most common childhood cancer with an excellent survival rate due to advancements in therapy. However, significant chemotherapy treatment-related toxicities (TRTs) are associated with the intensity of such treatments, which can affect quality of life, preclude the ability to provide optimal therapy, and impact survival. Further, outcomes are worse among certain minority populations, including Hispanic patients. At this single institution with a predominately Hispanic population, we sought to review several TRTs and determine whether Hispanic ethnicity may be a risk factor for increased severe, short-term TRTs and to explore the effects of TRTs on event-free survival (EFS).MethodsThis study is a retrospective chart-review of patients diagnosed with ALL at Children’s Hospital Los Angeles from January 2008 to December 2010. Infants, patients with Down’s syndrome and those who transferred to another institution during therapy were excluded from this study. Demographic and TRT information were collected from the electronic medical record, from the start of treatment until 30 days after the end of primary therapy, relapse, transplant, or death. TRTs were graded per the Common Terminology Criteria for Adverse Events version 4.0; only toxicities severe enough to negatively effect patients’ quality of life, chemotherapy continuation, and survival were included. The specific TRTs were fractures, osteonecrosis, and peripheral neuropathy of ≥ grade 2, fungal and culture-positive bacterial infections, thrombosis, pancreatitis, and hyperbilirubinemia ≥ grade 3, and hepatic transaminitis ≥ grade 4. The X2 test was used to compare the proportions of Hispanic and non-Hispanic patients with and without the selected TRTs. Univariable and multivariable Cox regression models were used to examine the association of patient demographics with EFS and time to TRT. All analyses were performed using a 2-sided test and completed using the statistical software Stata.ResultsOf the 172 patients diagnosed with ALL between 2008 and 2010, 138 patients are included in this study, 124 with B-cell ALL and 14 with T-cell ALL. Among the 138 patients, 57.2% were male, 24.6% were obese, 76.1% were Hispanic, and 58% were classified as high-risk by the NCI Rome criteria. The median age at diagnosis was 7.9 years (range 1.1 to 20). All patients were treated according to ongoing Children’s Oncology Group therapeutic studies. During the course of therapy, 23 patients relapsed, 3 developed secondary malignancy, and 2 patients died from infection. There were 156 TRTs observed in 85 patients, with 61.6% of patients experiencing one or more of the selected TRTs. The most common TRTs were infectious and gastrointestinal/hepatobiliary events. While Hispanic patients had 2.2 times higher frequency of pancreatitis than non-Hispanic patients and 1.8 times more hyperbilirubinemia, there were no statistically significant differences in the incidence of any TRTs by ethnicity. NCI high risk and older age were the only significant predictors of any TRT (p<0.001). Obesity was significantly associated with the development of pancreatitis and hyperbilirubinemia (p=0.01). Ethnicity, NCI risk, and ages were all predictive of EFS in the univariable analysis, with Hispanic ethnicity associated with 3.4-fold increase in risk of relapse and death when compared to non-Hispanics (p = 0.047). In the multivariable setting, NCI risk was the only significant predictor of EFS, although there was a trend in increased risk of relapse and death among Hispanic patients.DiscussionIn this relatively small cohort of patients, we did not identify ethnicity as a risk factor for increased TRTs during therapy for ALL, although certain TRTs such as pancreatitis and hyperbilirubinemia may be more common among Hispanic patients. As expected, Hispanic ethnicity, NCI risk, and age at diagnosis were risk factors for increased relapse and death. These results may suggest that additional factors, such as genetics, disease biology, or medication compliance, may play a more significant role in worse outcomes for Hispanic patients, rather than difference in tolerance of the treatment itself. Analyses of a larger cohort of patients are ongoing to confirm these results and to comprehensively analyze the determinants of pancreatitis and hepatic toxicity, and their interaction with obesity in Hispanic patients with ALL. [Display omitted] DisclosuresBhojwani:Amgen: Other: Blinatumumab global pediatric advisory board 2015.

Outcomes of Children, Adolescents, and Young Adults with Acute Lymphoblastic Leukemia Based on Blast Genotype at Diagnosis: A Report from the Children's Oncology Group

▪Survival for childhood acute lymphoblastic leukemia (ALL) now approaches 90% with risk adapted therapy based on National Cancer Institute risk group (NCI RG) at diagnosis, somatic lymphoblast genetics, and early response to therapy as measured by minimal residual disease (MRD). The Children’s Oncology Group AALL03B1 ALL Classification trial enrolled 11,145 children, adolescents, and young adults less than 31 years of age with newly diagnosed B- or T-lineage ALL between December 2003 and September 2011. Companion therapeutic trials for B-lineage ALL included AALL0331 (n= 5226) for NCI standard risk (SR-ALL)(age 1-10 years and white blood cell count (WBC) < 50,000/uL) and AALL0232 (n=2907] for NCI high risk (HR) ALL (age > 10 years or presenting WBC > 50,000/uL). Assessing outcome by lymphoblast genetics revealed statistically significant distributions of genotype and NCI RG, as well as differences in event-free and overall-survival (EFS, OS) (Table 1). Not surprisingly, favorable genetic groups of Trisomy 4/10/17 (TT) and ETV6/RUNX1 were significantly more common in NCI SR patients (p< 0.0001 for each) while those with unfavorable characteristics (MLL rearranged [MLLr], intrachromosomal amplification of chromosome 21 [iAMP21], BCR/ABL1 and hypodiploidy [n<44]) occurred more frequently in NCI HR patients (p<0.0001 for each). Event-free and OS were correspondingly poorer in NCI HR patients with the exception of iAMP21, where EFS in those treated on AALL0232 was better than that in NCI SR (Table 1). Surprisingly, NCI SR BCR/ABL1 positive patients (N= 64, 1.2%) had a 5-year EFS of 85±5.0%, although these patients came off study at end induction and likely received imatinib with chemotherapy on a companion ALL trial for Ph+ ALL. Notably, hypodiploidy was associated with the worst EFS and OS regardless of NCI RG, with 5-year EFS and OS of 51.3±5.0% and 58.2±5.0%, respectively, suggesting that these patients continue to fare poorly with salvage therapies. Multivariable analysis demonstrated age, WBC, and day 29 MRD as significant independent risk factors for sustained CR, and the individual genetic groups of TT, ETV6/RUNX1, iAMP21, BCR/ABL1 and hypodiploidy, but notably, not MLLr, all retained independent prognostic significance when added to the model individually.A subset of consecutively enrolled (N=605) AALL0232 NCI HR patients underwent additional genomic interrogation, including assessment of Ph-like status, ABL1 class fusions, CRLF2r, JAK mutations (JAKm), and IKZF1 alterations. Based on sample availability, patients studied were younger (p < 0.0001) and had a higher WBC (p < 0.0001) compared to the remainder of AALL0232. There were 85/605 (14.0%) Ph-like patients defined using PAM clustering algorithms and Ph-like status was significantly associated with an IKZF1 alteration (75%) (p < 0.0001) and day 29 MRD > .01% (p < 0.0001). Five-year EFS for Ph-like versus non Ph-like was 62.3±5.8% vs. 83.9±1.7% (p < 0.0001). Outcomes of Ph-like ALL with or without CRLF2r were similar (60.6±8.3% versus 65.4±8.0%, p =0.86). Similarly, 5-year EFS of Ph-like ALL was no different with or without IKZF1 alterations (61.5±7.0% vs. 64.6 ±11.1%). There were 155 (27.1%) IKZF1 alterations, 60 of which occurred in Ph-like ALL with a trend towards concomitant CRLF2r/JAKm (p=0.055). Five-year EFS for patients with IKZF1 alterations was 66.8±4.0% (p < 0.0001) versus 86.4±1.8% for those without IKZF1 lesions. Multivariable analysis demonstrated age, WBC and day 29 MRD as independent risk factors for sustained CR while only Ph-like status, IKZF1 alteration, BCR/ABL1 and ETV6/RUNX1retained independent prognostic significance when added to the model individually.In summary, somatic sentinel cytogenetic alterations are independently prognostic in childhood ALL and are strongly associated with NCI RG and outcome, supporting continued incorporation into risk stratification algorithms. Notably, >44% of all patients have favorable blast cytogenetics with 5-year overall survival rates approaching 100%. In contrast, NCI HR patients with Ph-like ALL have poor outcomes with currently available therapy and this subtype is associated with CRLF2 r and IKZF1 alterations, which do not confer an inferior EFS within the Ph-like subgroup. Novel therapies for genomicallydefined Ph-like ALL may improve outcomes. [Display omitted] DisclosuresLoh:Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees; Abbvie: Research Funding. Borowitz:HTG Molecular: Consultancy; Bristol-Myers Squibb: Research Funding; MedImmune: Research Funding; BD Biosciences: Research Funding.

Circulating CD2 Negative T Cells in Pediatric Acute Leukemia

Introduction: Leukemia cells are able to escape from immunosurveillance using immune tolerance mechanisms as the majority of leukemia antigens are either shared or aberrantly expressed self-proteins. T cells reactive to these antigens are purged during thymic selection. CD2, a pan-T-cell antigen, is expressed early during T cell developments in thymus and is found on all subsets of mature T cells. Recent studies show that there are low levels of extrathymic CD2 negative (CD2-) T cells, which show immature T cell features and can be induced to differentiate into mature helper and cytotoxic T cells in vitro. Since circulating CD2- T cells could represent pre-selection immature T cells, they may play an important role in tumor immunity.Methods: 81 pediatric B-cell acute lymphoblastic leukemia (B-ALL) patients, 22 pediatric acute myeloid leukemia (AML) patients and 22 normal controls were included in this study. B-ALL group included 45 NCI-standard risk (SR) patients and 36 NCI-high risk patients. All the leukemia patients were diagnosed at Children's Mercy Hospital in the past ten years with a diagnostic peripheral blood (PB) specimen. The PB specimens were studied by four-color multiparameter flow cytometry with antibodies for T cell markers (CD2, CD3, CD4, CD5, CD7 and CD8) and CD45, and analyzed by BD FACSDiva 8.0.1. CD2- and CD3+ T cells were recorded as % of total T cells. Student's t-test was used to compare results.Results: The percentages of CD2- T cells in AML (mean ± STD: 1.31% ± 1.41%) and B-ALL (0.84% ± 0.67%) were significantly higher than that seen in control group (0.51% ± 0.52%, p<0.05). No significant difference was found between AML and B-ALL. There was no significant difference between HR B-ALL (0.96% ± 0.81%) and SR B-ALL (0.74% ± 0.52%). Interestingly, CD2- T cells in 4/5 B-ALLs with 11q23 (KMT2A) rearrangement were undetectable. All 3 therapy-related AML patients studied had KMT2A gene rearrangement, and had no detectable CD2- T cells with poor clinical outcome (overall survival less than 1 year). The 3 AMLs associated with Down syndrome, a prognostically favorable AML group, showed relative high levels (≥ 1.49%) of CD2- T cells.Conclusions: Circulating CD2- T cells are increased in peripheral blood in pediatric AML and B-ALL patients. KMT2A gene rearrangement, an unfavorable cytogenetic abnormality, is associated with a decrease in CD2- T cells. The relationship of KMT2A gene rearrangement and decrease in circulating CD2- T-cells as well as the relationship of CD2- T cells to clinical outcome should be evaluated in future studies. The role of CD2- T cells in tumor specific immunomodulation should be explored, and may impact future studies of cell-based cancer immunotherapeutics. DisclosuresNo relevant conflicts of interest to declare.

Long Term Overall Survival of Greater Than 98% in Childhood ALL Patients with Good Risk Features and Low Risk MRD:Â Results from a Large Multi-Center Randomized Controlled Trial, UKALL 2003

Background: Overall survival (OS) for childhood ALL treated on contemporary protocols is now &gt; 90%. For low risk patients the risk of treatment related mortality (TRM) is now similar to the risk of death due to disease relapse. The only way to improve TRM and morbidity in this group is to identify even lower risk patients and reduce therapy. We analysed outcomes for patients with low risk MRD at end of induction (EOI) therapy treated on UKALL 2003, to identify a very low risk group who could potentially benefit from protocols that further reduce TRM. Methods: UKALL 2003 trial recruited 3126 patients aged 1-25 years with Philadelphia-negative ALL between Oct 1, 2003, and June 30, 2011. Treatment was initially stratified based on NCI risk and cytogenetic results. Subsequent treatment was directed by MRD from bone marrow (BM) measured using EuroMRD approved real-time quantitative PCR method for immunoglobulin and T-cell receptor gene rearrangements at EOI therapy. Analysis was performed on the 2666 patients with available MRD results and focused on patients with low risk MRD combined with other patient characteristics - cytogenetic risk group, white cell count (WCC) and age to identify those subgroups with extremely good event free survival (EFS). Low risk MRD at EOI was defined a level &lt;0.005%. Patients with MRD ≥ 0.005% were considered high risk. Good risk cytogenetics included the presence of ETV6-RUNX1 or high hyperdiploidy. Results: Overall 52% (n=1391) of patients had MRD &lt; 0.005% with the remaining 48% (n=1275) of patients with MRD ≥ 0.005%. 5yr OS 97.6 (95% CI 96.6-98.3) vs. 89.1% (87.2-90.7, p&lt;0.0001) and 5yr EFS 94.4 (93.1-95.6) vs. 83.6% (81.4-85.5, p&lt;0.0001). 53% (n=1407) of the patients with MRD results available had good risk cytogenetics, of which 60% (n=843) had MRD&lt;0.005%. This group (with low risk MRD and good risk cytogenetics) makes up 31.6% of the whole trial cohort and has 5yr EFS 96.0% (94.5-97.3) and 5yr OS 98.9% (97.9-99.4). The outcome was similar irrespective of NCI high risk features (i.e. WCC&gt;50 / age&gt;10yrs). Long term survival remained excellent with 10 year EFS 93.9% (OS 98.2%). There were 32 relapses in the low risk MRD/ good risk cytogenetics group (relapse sites: 11 BM, 7 combined BM and central nervous system (CNS), 3 BM + other site, 6 isolated CNS and 5 other site, non BM/CNS), giving an overall relapse rate of 3.8% with a salvage rate of 81%. The relapse death rate was 0.7% (n=6) with TRM of 0.8% (n=7). The low risk group can be further sub divided into a group of 442 patients (16.6% of whole trial) with undetectable MRD at EOI and good risk cytogenetics who have a 5yr EFS of 97.4% (5yr OS 99.5%). Conclusion: This excellent long term outcome for a third of all patients with childhood ALL, low risk MRD and good risk cytogenetics in a large multi-center randomized controlled trial supports exploration of further reduction of therapy in this group to reduce TRM. This strategy is further supported by the observation that the rate of TRM is now similar the relapse death rate in this group, coupled with the very high salvage rates for those patients who do relapse. The superior OS for patients with undetectable MRD and good risk cytogenetics further highlights the additive strength of MRD to accurately predict outcome in the low risk cytogenetic group. Disclosures No relevant conflicts of interest to declare.