High Minimal Residual Disease Levels Research Articles

Improved MRD Negativity Rates in Adverse Genomic Risk B-ALL Patients with Chemotherapy / Blinatumomab Induction: Experience from the Australasian Leukaemia Lymphoma Group (ALLG) ALL06/09 Studies

Introduction: Despite the benefits conferred by pediatric treatment protocols, outcomes in adolescent and young adult (AYA) acute lymphoblastic leukemia (ALL) remain inferior to children. Poor outcomes in AYA ALL have been associated with reduced tolerability of intensive cytotoxics and higher incidence of adverse risk disease. Our earlier ALLG ALL06 study demonstrated intensive pediatric induction/consolidation could be delivered in a similar time frame as in children suggesting tolerability was not a major contributor to poor outcome in AYA ALL. ALL06 established post consolidation (TP2=d79) minimal residual disease (MRD) positivity (MRD+) and high BMI was predictive of inferior disease free- and overall survival (OS). In order to improve TP2 MRD negativity (MRD-) in B-cell disease, the ALLG ALL09 study substituted standard consolidation for blinatumomab (blin) in phase I and II of a BFM-style protocol . We present the impact of blin on outcomes in genomic cohorts from ALL09 and compare these to similar cohorts from ALL06 treated with standard chemotherapy. Methods: Between Sep 2020 and Apr 2022, 55 patientswere enrolled to ALL09. Of these, 45 had appropriate samples for genomic analyses and 39/45 had an MRD marker identified. These 39 patients formed the genomic cohort presented below. Genomic subtyping was performed using whole transcriptome sequencing, MLPA, karyotype and FISH analyses, and disease was classified into genomic adverse (AR) vs standard (SR) risk based on contemporary literature classifiers. Bone marrow MRD was assessed using ASO-PCR for IGH and TCR rearrangements, at d33 post induction (TP1), and TP2 post blin consolidation. Differences in TP2 MRD were assessed, with estimated 3 yr relapse free survival (RFS) and OS calculated using the Kaplan-Meier method. Results: In the ALL09 cohort, median follow up was 629 days with 3 yr RFS 84.5% and OS 87.1%. In the genomic cohort, median follow up was 602 days with 3 yr RFS 88.8% and OS 93.2%, respectively. These compared favorably to 3 yr RFS and OS (both 67.5%) in the B-cell genomic cohort from ALL06. Between ALL09 and ALL06 there were similar proportions of AR patients (73% and 62.5%, respectively). In ALL09, the most frequent subtypes were PAX5alt (18%) and PAX5 p.P80R (11%) versus KMT2Ar and DUX4r (both 17.5%) in ALL06. In ALL09, Ph-like disease represented 13% vs 12.5% in ALL06. In the ALL09 genomic cohort, the MRD+ rate reduced between TP1 and TP2 (p< 0.001), with the reduction in the rate of positivity being more pronounced in the AR cohort (AR MRD+ TP1=85% vs AR TP2=39%; p< 0.001). In contrast, in ALL06 MRD+ in the AR cohort reduced by only 28% between TP1 and TP2 (p >0.05). This suggests a positive impact of blin consolidation in AR patients in ALL09. Despite improved AR MRD+ rates overall, not all genomic subtypes in ALL09 followed this trend (Table 1). To date, there are 5 relapses in the ALL09 cohort, 4 from the genomic cohort. Of these, 1 was hypodiploid and strikingly the remaining 3 patients harbored a TCF3 rearrangement ( TCF3r). All 4 relapses were significantly associated with MRD+ at TP2 (RFS: MRD-, 100% (n=14) vs MRD+, 71% (n=25); p= 0.013), and all were observed in the AR genomic group. Of interest, the fifth case, outside of the genomic cohort, was classified as PAX5alt. In ALL09, high-risk (HR) patients proceeded to intensive HR block chemotherapy with the aim of eliminating MRD prior to allogeneic transplant (SCT). In the genomics cohort 15 patients proceeded to HR therapy, n=12 were considered AR. Sustained MRD+ through HR blocks 1 and 2 was noted in patients harboring PAX5 p.P80R (3/3), KMT2Ar (2/2) and TCF3r (2/3). Of the 9 patients who proceeded to SCT, 3 had PAX5 p.P80R 1 had PAX5alt, 2 were KMT2Ar and there was 1 each of DUX4r, hypodiploid and TCF3r. The 3 patients who remained MRD+ in the SR cohort had PAX5 p.P80R and all 3 proceeded to SCT. Conclusion: This is the first report of the impact of blin consolidation on genomic subsets of de novo AYA ALL. Our study suggests blin sensitivity as assessed by TP2 MRD response may be genomic subtype dependent, with TCF3r associated with sustained MRD+, leading to eventual relapse (3/3 patients). In addition, the PAX5 p.P80R subset was also associated with sustained high levels of TP2 MRD+ (3/4 with an MRD marker) and SCT (3/5 patients). These results may assist with identification of AYA ALL subsets that could benefit from alternative approaches as blin becomes increasingly incorporated into front-line protocols.

P374: BLINATUMOMAB AS CONSOLIDATION FOR ADULT B-CELL PRECURSOR ACUTE LYMPHOBLASTIC LEUKEMIA. A REAL-WORLD STUDY

Background: Blinatumomab is a CD3/CD19 bispecific T-cell engager approved for the treatment of relapsed/refractory (R/R) or minimal residual disease (MRD)-positive B-cell precursor acute lymphoblastic leukemia (B-ALL). Recent phase 3 studies in children and young adults with B-ALL in first relapse suggested that blinatumomab used as consolidation after chemotherapy salvage could be more beneficial than given as single agent in overt relapse. Whereas current strategies aim to demonstrate the benefit of blinatumomab in first line, the optimal use of blinatumomab in adult patients with first B-ALL relapse still deserves to be further explored Aims: To evaluate the efficacy of blinatumomab given as consolidation in adults with B-ALL in a real-world setting Methods: We retrospectively included 115 consecutive patients with B-ALL treated with blinatumomab from April 2012 until June 2021 at Saint-Louis Hospital, Paris, France (n=100), and at AOU Città della Salute e della Scienza, Turin, Italy (n=15). Patients included in clinical trials were excluded. Patients were divided in three subgroups: 68 patients treated in 1st complete remission (CR1), 31 patients treated in 2nd CR after chemotherapy-base salvage therapy (CR2), and 16 patients treated in overt relapse (R/R). Patients in CR1 received blinatumomab for MRD persistence (n=59/68, 87%) or due to inability to receive standard consolidation (n=9/68, 13%, off-label use). The number of blinatumomab cycles along with the use of chemotherapy and/or of allogeneic hematopoietic stem cell transplant (alloHSCT) after blinatumomab was up to physician choice. Results: The median age of patients was 37 years (range, 15-84). Among the 115 patients, 24% (n=28) were Philadelphia (Ph)-positive. Age, sex, baseline disease features and genetic risk categories did not differ between subgroups. After blinatumomab a complete MRD-response was achieved in 83% of CR1 and 86% of CR2 patients (p=.99). A complete remission was reached by 9/15 R/R patients (60%). In the 3 subgroups, the median number of blinatumomab cycles given was 2 (range, 1-6). Forty-six patients (42%) treated in CR (41% CR1, 45% CR2) and 4 R/R patients (25%) were bridged to allo-HSCT in continuous CR after blinatumomab. With a median follow up of 3.1 years, 3-year DFS was 68% in CR1 and 67% in CR2 patients (p=0.41); 3-year OS was 80% in CR1 and 71% in CR2 patients (p=0.32). In R/R patients, 3-year DFS and OS were 13% and 20% respectively. Considering patients who received blinatumomab in CR (CR1+CR2), univariate analysis showed that higher MRD levels both before and after blinatumomab were associated with shorter DFS, while only MRD response to blinatumomab was associated with OS. Both pre- and post-blinatumomab MRD levels retained significance in bivariate analysis for DFS Image:Summary/Conclusion: The present study underlines the efficacy of blinatumomab in consolidation after chemotherapy-based salvage, showing comparable outcomes between patients treated in CR2 and CR1. In CR2 patients, promising DFS and OS were observed as compared to historical cohorts of patients treated with chemotherapy alone or with blinatumomab in overt relapse. Our data suggest that blinatumomab should be preferably used in consolidation rather than as salvage therapy in patients with B-ALL in first relapse

High tumor burden before blinatumomab has a negative impact on the outcome of adult patients with B-cell precursor acute lymphoblastic leukemia. A real-world study by the GRAALL.

Blinatumomab is a bispecific T-cell engager approved for B-cell precursor acute lymphoblastic leukemia (B-ALL) with persistent minimal residual disease (MRD) or in relapse. The prognostic impact of tumor load has been suggested before other immunotherapies but remains poorly explored before blinatumomab. We retrospectively analyzed the outcome of 73 patients who received blinatumomab either in first complete remission (CR) with MRD (n=35) or at relapse (n=38). Among MRD patients, 91% had MRD >0.01% before blinatumomab, and 89% achieved complete MRD response after blinatumomab. High pre-blinatumomab MRD levels were associated with shorter relapse-free survival (P=0.049) and overall survival (OS) (P=0.011). At 3 years, OS was 33%, 58% and 86% for pre-blinatumomab MRD >1%, between MRD 0.1-1% and <0.1% respectively. Among relapsed patients, 23 received blinatumomab with overt relapse and 15 were in complete response (CR) after bridging chemotherapy. At 3 years, overall CR rate was 68% and complete MRD response rate was 84%. Patients who directly received blinatumomab had shorter relapse-free survival (P=0.033) and OS (P=0.003) than patients bridged to blinatumomab. Three-year OS was 66% in the latter group compared to 16% in the former group. Our observations suggest that pre-blinatumomab tumor burden should help to design more tailored strategies including tumor load reduction in relapsed patients.

Prognostic significance of IKZF1 deletions and IKZF1plus profile in children with B-cell precursor acute lymphoblastic leukemia treated according to the ALL-IC BFM 2009 protocol.

The strongest predictors of outcome in pediatric B-cell precursor acute lymphoblastic leukemia (BCP-ALL) are minimal residual disease (MRD) and specific molecular abnormalities. One unfavorable prognostic factor is the presence of IKZF1 gene aberrations, particularly when co-occurring with high MRD level at the end of induction treatment. The present study determines the predictive value of a recently-defined IKZF1-plus (IKZF1plus ) microdeletion profile in 373 children with BCP-ALL treated according to the ALL-intercontinental Berlin-Frankfurt-Munster protocol 2009 protocol. IKZF1-wild type (IKZF1wt ) patients demonstrated lower leukemic burden parameters than those carrying IKZF1 deletion (IKZF1del [n=26, 7.0%]) or IKZF1plus pattern (n=34, 9.1%): (i) median blast percentage at diagnosis (78.0% vs. 86.9% vs. 86.0%; p=0.021); (ii) median MRD level at day 15 of induction protocol (0.3% vs. 2.1% vs. 0.8%; p=0.011); (iii) poor steroid response (7.6% vs. 26.5% vs. 12.5%; p=0.010). Minimal residual disease level at day 33 (MRD33) exceeding 10-4 was more frequently observed in both the IKZF1del and IKZF1plus subgroups than in IKZF1wt patients (n=9 [36.0%] vs. n=13 [41.9%] vs. n=70 [24.0%], p=0.051). IKZF1plus individuals showed a tendency for a lower MRD reduction between day 15 and 33 compared to IKZF1del patients (p=0.124). IKZF1del and IKZF1plus patients showed decreased relapse-free survival (HR [95%CI] for IKZF1wt as reference=2.72 [1.21-6.11] and 2.00 [0.87-4.49], respectively, p=0.023). Both genetic markers including IKZF1del and IKZF1plus microdeletion profile provide additional predictive value of treatment outcome in childhood BCP-ALL and may contribute to more efficient patient stratification; the same is true in MRD guided protocols, which are based on flow cytometric measurements on day 15 of induction protocol.

Preemptive Immunotherapy for Minimal Residual Disease in Patients With t(8;21) Acute Myeloid Leukemia After Allogeneic Hematopoietic Stem Cell Transplantation.

In patients with t(8;21) acute myeloid leukemia (AML), recurrent minimal residual disease (MRD) measured by RUNX1-RUNX1T1 transcript levels can predict relapse after allogeneic hematopoietic stem cell transplantation (allo-HSCT). This study aimed to compare the efficacy of preemptive interferon (IFN)-α therapy and donor lymphocyte infusion (DLI) in patients with t(8;21) AML following allo-HSCT. We also evaluated the appropriate method for patients with different levels of RUNX1-RUNX1T1 transcripts. In this retrospective study, consecutive patients who had high-risk t(8;21) AML and received allo-HSCT were enrolled. The inclusion criteria were as follows: (1) age ≤65 years; (2) regained MRD positive following allo-HSCT. MRD positive was defined as the loss of a ≥4.5-log reduction and/or <4.5-log reduction in the RUNX1-RUNX1T1 transcripts, and high-level, intermediate-level, and low-level MRDs were, respectively, defined as <2.5-log, 2.5−3.5-log, and 3.5−4.5-log reductions in the transcripts compared with the pretreatment baseline level. Patients with positive RUNX1-RUNX1T1 could receive preemptive IFN-α therapy or DLI, which was primarily based on donor availability and the intentions of physicians and patients. The patients received recombinant human IFN-α-2b therapy by subcutaneous injection twice a week every 4 weeks. IFN-α therapy was scheduled for six cycles or until the RUNX1-RUNX1T1 transcripts were negative for at least two consecutive tests. The rates of MRD turning negative for patients with low-level, intermediate-level, and high-level RUNX1-RUNX1T1 receiving IFN-α were 87.5%, 58.1%, and 22.2%, respectively; meanwhile, for patients with intermediate-level and high-level RUNX1-RUNX1T1 receiving DLI, the rates were 50.0% and 14.3%, respectively. For patients with low-level and intermediate-level RUNX1-RUNX1T1, the probability of overall survival at 2 years was higher in the IFN-α group than in the DLI group (87.6% vs. 55.6%; p = 0.003). For patients with high levels of RUNX1-RUNX1T1, the probability of overall survival was comparable between the IFN-α and DLI groups (53.3% vs. 83.3%; p = 0.780). Therefore, patients with low-level and intermediate-level RUNX1-RUNX1T1 could benefit more from preemptive IFN-α therapy compared with DLI. Clinical outcomes were comparable between preemptive IFN-α therapy and DLI in patients with high-level RUNX1-RUNX1T1; however, they should be further improved.

Genome-Wide Association Study (GWAS) of High-Risk Minimal Residual Disease and Relapse in B-Cell Acute Lymphoblastic Leukemia on Trial AIEOP-BFM ALL 2000

▪A significant proportion of patients with pediatric acute lymphoblastic leukemia (ALL) still suffers from relapse and therapy-related toxicities. Thus, the focus of further improvement of therapy for them is not only cure, but minimizing both short-term and long-term therapy-associated toxicity. This can be achieved by better personalized adjustment of therapy to the risk of relapse. Continuing research has identified numerous features with prognostic potential, including clinical and genetic variables as well as early response to chemotherapy being associated with treatment outcome. While most research activities on genetic prognostic factors have focused on somatic features, relatively little is known on hereditary contributions to treatment response and outcome in pediatric ALL. Therefore, we conducted a genome-wide association study (GWAS) of high-risk minimal residual disease (MRD) and relapse in B cell precursor (BCP) ALL patients treated on trial AIEOP-BFM ALL 2000.On this trial, patients were stratified into three risk groups, mainly by MRD analyses. MRD standard-risk (MRD-SR) patients were MRD-negative on treatment days 33 and 78, MRD high-risk (MRD-HR) patients had residual disease of ≥5x10-4 on treatment day 78. All the remaining MRD results were considered MRD intermediate-risk (MRD-IR). Besides MRD, established high-risk parameters were also retained for stratification: prednisone poor-response, induction failure, positivity for t(4;11)/ MLL-AF4 . Treatment used standard drugs and, in some of the patients, cranial irradiation and/or hematopoietic stem cell transplantation. DNA isolated from remission samples was genotyped using Illumina Human1M-Duo BeadChips containing 1.048.711 single SNV markers. For GWAS analyses gPLINK v2.050, PLINK v.1.09 and RStatistics v3.3.1 were used. The analysis on MRD was conducted in 69 MRD-HR patients (cases) and in 1034 patients of the MRD-SR and MRD-IR groups (controls). The analysis on relapse employed 145 relapsed (cases) and 1007 non-relapsed patients (controls). After quality control assessment, the final analyses included 749.262 SNPs among 62 MRD-HR patients compared to 927 controls and 129 relapsed patients compared to 925 controls.In the analysis on MRD-HR five SNVs reached genome-wide significance at P ≤5×10−8. An intronic SNV (rs1570765) in STARD13 demonstrated the strongest association (P =1.73x10-10; odds ratio, OR=5.06). Two additional SNVs with P ≤5×10−8 in STARD13 were in linkage disequilibrium with rs1570765. The two remaining SNVs with P ≤5×10−8 were located in FEZ2 and NRIP1. Five additional SNVs demonstrated significant levels of ≤1×10−6 and were associatedwith the following genes: STARD13 , VIT and FICD . STARD13 is located on chromosome 13, belongs to the family of RhoGap proteins and is frequently lost in hepatocellular and breast carcinomas. Its RhoGAP domain activates members of the Ras superfamily which leads to a suppression of cell growth and differentiation (Lin et al. Oncogene 2010). In the GWAS approach on relapse three SNVs reached significant levels of ≤1×10−6 and were associatedwith the genes ASB3 (rs1549749, P =3.51x10-7; rs12465316, P =4.26x10-7) on chromosome 2 and NDN (rs9972595, P =1.04x10-6) on chromosome 15. Twenty additional SNVs demonstrated significance levels of ≤1×10−5. ASB3 codes for a member of the ankyrin repeat and SOCS box-containing (ASB) family of proteins containing ankyrin repeat sequence and a SOCS box domain. The latter serves to couple suppressor of cytokine signalling (SOCS) proteins and their binding partners with the elongin B and C complex, possibly targeting them for degradation. NDN , a p53 target gene, codes for Necdin which was previously shown to regulate the quiescence and response to genotoxic stress of hematopoietic stem/progenitor cells (Asai et al., Blood 2012). Further replication results, an analysis of additive effects and multivariate analyses will be presented.In conclusion, our results demonstrate that germline genetic variation is associated with high levels of MRD after induction/consolidation treatment for ALL and relapse on an AIEOP-BFM ALL protocol. In line with previous studies (Yang et al., JAMA 2009), our data suggest that genome-wide approaches may be useful to identify novel and clinically relevant SNVs for further refinement of risk-adapted treatment strategies in pediatric ALL. DisclosuresSchrappe:JAZZ Pharma: Consultancy, Research Funding; SigmaTau: Consultancy, Research Funding; Medac: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Baxalta: Consultancy, Research Funding.

Prognostic Value of Minimal Residual Disease in Children with Acute Lymphoblastic Leukemia.

Purpose To assess the prognostic value of determination of minimal residual disease in the bone marrow after multiagent remission induction therapy in children with acute lymphoblastic leukemia. Methods From September 2001 to December 2004, 102 patients with newly diagnosed B-cell precursor acute lymphoblastic leukemia were enrolled on protocol ALL-XH-99. Minimal residual disease in the bone marrow at the end of remission induction therapy, before high-dose methotrexate, early intensification as well as 1 year, 2 year of maintains therapy was detected by multi-parameter flow cytometry with various combinations of monoclonal antibodies for leukemia-associated immunophenotype. The probability of event-free survival was estimated by Kaplan-Meier analysis and the distributions of probability of event-free survival (pEFS) were compared using the log-rank test. Chi-square analysis or Fisher exact test were used to compare differences in the distribution of biologic presenting features. A Cox proportional hazards model was used to identify independent prognostic factors. Results [circ1] The probability of 39-month event-free survival (EFS) was significantly worse for patients who achieved a minimal residual level ≥ 0.01% in the bone marrow on the remission date as compared to that of other patients with a minimal residual level < 0.01% (0.00% vs 83.00±9.90%, P=0.0000). [circ2]Univariate analysis indicated that there were no relationship between level of minimal residual disease at the date of complete remission and biologic presenting features (gender, age, white blood cells), but did Philadelphia chromosome, ALL-XH-99 risk groups as well as lymphoblasts in the bone marrow on day 19 (P<0.05). [circ3] Multivariate analysis suggests patients with high level minimal residual disease after the first induction course was an independent prognostic factor (hazard ratio, 5.381; 95% confidence interval 0.004 to 0.624; P=0.020). Conclusions Early treatment response as assessed by minimal residual leukemia determination by flow cytometry has important prognostic significance and can be performed in a resource-poor patient population. Patients with level of minimal residual disease ≥ 0.01% at end of remission induction ought to be used an novel and more intentive chemotherapy.

The Value of CD44+ Mononuclear Cells and Spleen Stiffness Measurement in Minimal Residual Disease in Acute Myeloid Leukemia and Its Prognosis

To investigate the value of CD44+ mononuclear cells (MNC) and spleen stiffness measurement (SSM) in minimal residual disease (MRD) in acute myeloid leukemia (AML) and its prognosis. Flow cytometry was used to detected the proportion of CD44+ and CD24+ MNC in 44 AML patients after induction chemotherapy. The SSM was tested by FS. The value of MNC and SSM in MRD and its prognosis was explored. The percentage of CD44+ MNC and SSM in MRD positive group were significantly higher than those in MRD negative group (P<0.05). In MRD positive group, there were positive correlation between CD44+ MNC, SSM and MRD level (r=0.998, r=0.939, P<0.05). The median EFS and OS in HCD44+ MNC and HSSM groups were significantly shorter than those in LCD44+ MNC and LSSM (P<0.05). CD24+ MNC showed no association with MRD and its prognosis. HCD44+ MNC and HSSM may be used to predict high level MRD and poor prognosis.

Relationship between Leukocytes Derived Microparticles and Minimal Residual Disease and Prognosis of Acute Myeloid Leukemia

To detect the relationship between leukocytes derived microparticle (CD45+ MP) and minimal residual disease (MRD) and prognosis of acute myeloid leukemia (AML). The expression of CD45+ MP, CD44+ MP and CD24+ MP in peripheral blood of 47 AML patients at the time after induction chemotherapy were detected by using flow cytometry, and the relationship between MP, MRD and prognosis were analyzed. The percentages of CD45+ MP, CD44+ MP and CD24+ MP in MRD positive group were significantly higher than those in MRD negative group. In MRD positive group, there were positive correlation between CD45+ MP, CD44+ MP, CD24+ MP and MRD level. The AUC of CD45+ MP, CD44+ MP, CD24+ MP in predicting positive MRD was 0.949, 0.782, and 0.817, respectively. The EFS and OS in HCD45+ MP, HCD44+ MP and HCD24+ MP groups were significantly shorter than low level group. High level of CD45+ MP, CD44+ MP, CD24+ MP can be used to predict high level MRD and poor prognosis.

Clinical Implications of Minimal Residual Disease Detection in Infants With KMT2A-Rearranged Acute Lymphoblastic Leukemia Treated on the Interfant-06 Protocol.

PURPOSEInfant acute lymphoblastic leukemia (ALL) is characterized by a high incidence of KMT2A gene rearrangements and poor outcome. We evaluated the value of minimal residual disease (MRD) in infants with KMT2A-rearranged ALL treated within the Interfant-06 protocol, which compared lymphoid-style consolidation (protocol IB) versus myeloid-style consolidation (araC, daunorubicin, etoposide/mitoxantrone, araC, etoposide).MATERIALS AND METHODSMRD was measured in 249 infants by DNA-based polymerase chain reaction of rearranged KMT2A, immunoglobulin, and/or T-cell receptor genes, at the end of induction (EOI) and end of consolidation (EOC). MRD results were classified as negative, intermediate (< 5 × 10−4), and high (≥ 5 × 10−4).RESULTSEOI MRD levels predicted outcome with 6-year disease-free survival (DFS) of 60.2% (95% CI, 43.2 to 73.6), 45.0% (95% CI, 28.3 to 53.1), and 33.8% (95% CI, 23.8 to 44.1) for infants with negative, intermediate, and high EOI MRD levels, respectively (P = .0039). EOC MRD levels were also predictive of outcome, with 6-year DFS of 68.2% (95% CI, 55.2 to 78.1), 40.1% (95% CI, 28.1 to 51.9), and 11.9% (95% CI, 2.6 to 29.1) for infants with negative, intermediate, and high EOC MRD levels, respectively (P < .0001). Analysis of EOI MRD according to the type of consolidation treatment showed that infants treated with lymphoid-style consolidation had 6-year DFS of 78.2% (95% CI, 51.4 to 91.3), 47.2% (95% CI, 33.0 to 60.1), and 23.2% (95% CI, 12.1 to 36.4) for negative, intermediate, and high MRD levels, respectively (P < .0001), while for myeloid-style–treated patients the corresponding figures were 45.0% (95% CI, 23.9 to 64.1), 41.3% (95% CI, 23.2 to 58.5), and 45.9% (95% CI, 29.4 to 60.9).CONCLUSIONThis study provides support for the idea that induction therapy selects patients for subsequent therapy; infants with high EOI MRD may benefit from AML-like consolidation (DFS 45.9% v 23.2%), whereas patients with low EOI MRD may benefit from ALL-like consolidation (DFS 78.2% v 45.0%). Patients with positive EOC MRD had dismal outcomes. These findings will be used for treatment interventions in the next Interfant protocol.

Minimal residual disease in adolescent (older than 14 years) and adult acute lymphoblastic leukemias: early immunophenotypic evaluation has high clinical value

AbstractInvestigation of minimal residual disease (MRD) in acute leukemias by immunophenotyping and/or molecular techniques is proving to be increasingly valuable for disease monitoring. In acute lymphoblastic leukemia (ALL), most MRD studies have focused on children, whereas in contrast, information on the value of MRD on adult ALL is scanty, and almost exclusively restricted to polymerase chain reaction (PCR) studies. Early response to therapy is one of the most important prognostic factors in acute leukemia, which prompted us to investigate whether or not early immunophenotypic assessment of MRD could also be a valuable tool for predicting relapse in adult patients with ALL. For that purpose we have analyzed the level of MRD during the initial phase of treatment (induction phase) by multiparameter flow cytometry in a series of 102 adolescent (older than 14 years) and adult patients with ALL. Immunophenotypic evaluation of the bone marrow (BM) at day +35 showed that patients with low MRD levels (< 0.05% leukemia-associated phenotype [LAP+] cells) had a significantly longer relapse-free survival (RFS) than patients with high MRD levels, and this prognostic influence was retained when only those patients in morphologic complete remission (mCR) at day +35 were considered (median RFS: 42 months vs 16 months; P = .001). Moreover, immunophenotyping helped to identify a small subset of patients (n = 12) with negative or low MRD levels (< 0.03% LAP+ cells) by day +14, with an excellent prognosis (projected RFS of 90% at 5 years). The contrary is true of patients who achieved late mCR (after day +35), since immunophenotypic investigation of MRD showed that, in spite of the mCR, none of the cases with more than 0.1% LAP+ cells would be relapse-free after 2 years. Multivariate analysis showed that the immunologic evaluation of MRD at day +35 was the most relevant independent prognostic parameter for adult patients with ALL, and together with age, white blood cell (WBC) count at diagnosis, and presence of the Philadelphia (Ph) chromosome, represented the most informative combination of variables for predicting relapse-free survival.

Clinical Implications of Minimal Residual Disease Detection in Infants with KMT2A-Rearranged Acute Lymphoblastic Leukemia Treated on the Interfant-06 Protocol

Purpose Infant acute lymphoblastic leukemia (ALL) is characterized by KMT2A gene rearrangements and a poor outcome. Therefore, infants are treated with specific protocols. In older children, minimal residual disease (MRD) is used for risk group stratification. In infant ALL, data on MRD are scarce. We evaluated the prognostic value of MRD in a large series of infants with KMT2A rearranged ALL, treated within Interfant-06 in order to establish how to use MRD in these patients. This protocol included a randomization between lymphoid-style consolidation (protocol IB) versus a myeloid-style consolidation (ADE/MAE). Patients and methods MRD was measured in 249 infants with KMT2A-rearranged ALL by DNA-based PCR of rearranged KMT2A, immunoglobulin and/or T-cell receptor genes, at end of induction (EOI) (n=210), end of consolidation (EOC) (n=173) and after MARMA (n=164). MRD results were classified as negative, intermediate (&amp;lt;5x10-4), and high (≥5x10-4). Results In samples with both data on KMT2A MRD PCR and IG/TR MRD targets available (n=223), results were concordant in 94% (n=210/223) of samples. EOI MRD levels predicted outcome with 6-year disease free survival (DFS [SE]) of 60.2% (7.9), 45.0% (5.6), 33.8 % (5.3), for infants with negative, intermediate and high EOI MRD levels, respectively (p=0.0039). Strikingly, when analyzing MRD results according to consolidation treatment given, MRD levels at EOI predicted treatment outcome for patients treated with lymphoid-style consolidation, but not for patients treated with myeloid style consolidation. In patients treated with lymphoid-style consolidation 6-year DFS (SE) was 78.2% (9.8), 47.2% (7.1), 23.2% (7.1) for negative, intermediate and high MRD levels, (figure 1a) respectively (p&amp;lt;0.0001), whilst in myeloid-style treated patients the corresponding figures were 45.0% (10.7), 41.3% (9.4) and 45.9% (8.2) (figure 1b) This implies that patients with low EOI MRD benefit from protocol IB lymphoid consolidation (DFS 78.2% versus 45.0%, figure 1c), while patients with high MRD benefit from ADE/MAE myeloid consolidation (DFS 45.9% versus 23.2%, figure 1d)). In line with these findings, co-expression of myeloid markers was found in a higher percentage of patients with high EOI MRD (81%) versus those with low EOI MRD (50%) (p=0.0186). EOC MRD levels were also predictive of outcome, with 6-year DFS of 68.2 %(5.8), 40.1% (6.2), 11.9% (8.7) for infants with negative, intermediate and high EOC MRD levels respectively (p&amp;lt;0.0001). Patients that had positive EOI MRD and became negative at EOC also had a good outcome (6-DFS (SE) 65.7% (7.8)) Conclusion Induction therapy selects infant ALL patients for the type of subsequent therapy; infants with high EOI MRD benefit from AML-like consolidation, whereas patients with low MRD benefit from ALL-like consolidation. This hypothesis is further supported by the more pronounced expression of myeloid markers in patients with high EOI MRD levels. Patients with positive EOC MRD had dismal outcomes. These findings will be used for treatment interventions in the next Interfant protocol. Disclosures Brethon: Amgen: Other: invitation to meetings, remunerations for oral presentations, advices for the record of Blinatumomab in pediatrics in France. Locatelli:Jazz Pharmaceeutical: Speakers Bureau; Medac: Speakers Bureau; Miltenyi: Speakers Bureau; Bellicum Pharmaceutical: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Amgen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau.

Treating MRD Positivity in Multiple Myeloma: An Allogeneic GM-CSF-Based Vaccine in Combination with Lenalidomide Induces Long-Term Remissions in Patients with Low Disease Burden

Introduction: Novel therapies have increased the complete response (CR) rates in multiple myeloma (MM) with corresponding improvement in progression free survival (PFS). However, relapse occurs in a significant number of patients. Emerging evidence strongly correlates minimal residual disease (MRD) negativity with improved clinical outcome. Nonetheless, definitive clinical guidance on the management of MRD-positive MM is currently lacking. Here we present the results of a phase II trial evaluating an allogeneic GM-CSF vaccine in combination with lenalidomide (Len) in patients with MM in near CR (NCT01349569). Methods: To be enrolled, patients required a sustained near CR (defined as no measurable M-spike and positive immunofixation, IFE) for at least four months while on a Len-containing regimen. The vaccine consisted of two allogeneic, commercially available MM cell lines (U266 and H929) coupled to a GM-CSF producing leukemia cell line (K562, GVAX®). Patients received four vaccinations over 6 months in combination with Len maintenance for at least 1 year, although in most patients Len was continued until disease progression. The primary endpoints of this trial were eradication of detectable disease and conversion to CR. The secondary endpoints were safety, time to response and immune monitoring of vaccine- and MM-specific T cell responses. Bone marrow (BM) and peripheral blood (PB) samples were collected at pre-established timepoints and cryopreserved for subsequent analyses. The ImmunoSEQ® assay (AdaptiveBiotechnologies, Seattle, WA) was used to sequence T cell receptors (TCR) and the resulting data was used to analyze TCR repertoire metrics. The ImmunoSEQ® assay was also used to sequence the IGH and IGK/L B-cell receptors for MRD quatification. Deep phenotyping of T cells and immune monitoring were performed by flow cytometry. Results: Fifteen MM patients were enrolled. The primary enpoint of the trial was met as 53% (n = 8/15) of patients converted to a true CR (negative IFE) at a median time of 11.6 months (p = 0.011 when compared to the 25% threshold for futility). With a median follow-up of 5.13 years from enrollment, the median PFS could not be estimated as only 6 patients (40%) experienced disease relapse. At the time of the analysis, the median OS was 7.8 years from enrollment (95% CI: 4.2-7.8 years, n = 6/15, 40%). MRD testing was performed on 7 patients. The disease burden threshold of 105/106 cells was arbitrarily used to evaluate the clinical significance of high-level and low-level MRD positivity. Interestingly, all 3 patients with high-level MRD experienced relapse within 1 year of vaccination (median = 4.8 months, range: 2.8 - 9.5 months), while median PFS for low-level MRD patients was significantly prolonged (median = 84.15 months, range: 51.9 - 97.3 months, p = 0.01). Consistently, high-level MRD was associated with increased likelihood of clinical relapse (hazard ratio, HR = 25.79, 95% CI: 2.17 - 306.4). Immune phenotyping of BM CD8+ T cells identified a CD27- DNAM1-/low subpopulation whose abundance was associated with prolonged MM remission. This subset included senescent, effector and exhausted CD8+ T cells and was nearly absent in patients with high-level MRD. Analysis of T-cell repertoires identified vaccine-specific T-cell clonotypes that expanded in both BM and PB of all patients and persisted for up to seven years. Accordingly, polyfunctional T cell responses against vaccine-specific and MM-related antigens were increased and persisted 7 years after enrollment. Despite the correlation between MRD negativity and improved clinical outcome, 47% of patients subsequently developed a detectable M-spike that did not meet criteria for disease relapse nor required any change in treatment. We identified a bone marrow-resident T cell population likely responsible for the establishment of an immune equilibrium mediating long-term disease control. Conclusions: Collectively, these data demonstrate that an allogeneic MM vaccine in combination with Len effectively stimulates antitumor immunity and supports long-term remissions. Although MRD negativity is a critical factor in maintaining remission, the establishment of a MM-MGUS immune equilibrium is likely crucial in the setting of MRD+ MM to prevent disease progression. To our knowledge, this is the first study attempting to treat MRD+ MM in an effort to further improve disease response as well as prevent relapse. Disclosures Sanders: Adaptive Biotechnologies: Current equity holder in private company. Ali:Celgene: Membership on an entity's Board of Directors or advisory committees. Noonan:Aduro: Patents &amp; Royalties. Borrello:WindMIL Therapeutics: Other: Founder , Research Funding; Aduro: Patents &amp; Royalties; Celgene: Research Funding.

Ibrutinib Plus Fludarabine, Cyclophosphamide, and Rituximab As the Treatment for Chronic Lymphocytic Leukemia/ Small Lymphocytic Leukemia: A Single-Center Real World Study

Purpose: To evaluate the safety and efficacy of ibrutinib plus fludarabine, cyclophosphamide, and rituximab (iFCR) as the treatment for chronic lymphocytic leukemia (CLL)/ small lymphocytic leukemia (SLL) patients, we conducted time-limited, minimal residual disease (MRD)-driven real world study in The First Affiliated Hospital of Nanjing Medical University Methods: We enrolled patients aged 18 to 65 years old with CLL/SLL who required treatment. Oral Ibrutinib was given continuously (420 mg/day) from day 0, and patients were administered intravenously rituximab (375mg/m2 in day 0 of cycle 1; 500mg/m2 in day 0 of cycle 2-3), fludarabine (25mg/m2, days 1-3) and cyclophosphamide (250mg/m2, days 1-3), every 28-day cycles. All the patients received 3 cycles of iFCR in the first stage. Interim analysis was done according to the 2018 iwCLL criteria and MRD was detected by flow cytometry. Patients who achieved complete response (CR) or partial response (PR) with low MRD level (L-MRD, 10-4-10-2) or undetectable MRD (uMRD) level (&amp;lt;10-4) in peripheral blood (PB) were given 3 times of rituximab or the 4th cycle of iFCR, and then turned to ibrutinib maintenance. Patients who achieved PR with high MRD level (&amp;gt;10-2) in PB or bone marrow (BM), or with diameter of residual lymph node larger than 3cm were administered another 3 cycles of iFCR (6 in all) and followed by ibrutinib maintenance. The primary endpoint was the proportion of patients who achieved uMRD in the PB after 3 cycles of iFCR. The secondary endpoint was overall response rate (ORR), complete response rate (CR) and the number of adverse events (AE). Results: Between May 2019 and June 2020, 29 CLL/SLL patients were enrolled in this cohort with 27 CLL and 2 SLL. 26 of patients were the previously untreated and 3 of patients were relapse or treated before. The median age of patients was 53 years old. Unmutated IGHV was detected in 14 (50.0%) of 29 patients, 4 patients had del(17p) and/or TP53 mutation (13.8%), 7 patients had del(11q) (24.1%), 7 had NOTCH1 mutation (24.1%) and 7 had MYD88 mutation (24.1%). 8 patients (30.8%) were classified as low-risk group according to CLL-IPI, with 9 in intermediate-risk group (34.6%), 5 in high-risk group (19.2%) and 4 in very-high risk group (15.4%). At data cutoff (1st July, 2020), the median follow-up and treatment time was seven months (1-13 months) with 23 patients had completed at least two cycles of iFCR. At interim analysis, the ORR was 100% with 8 patients achieved CR (34.8%), 3 achieved CRi (13.0%) and 12 achieved PR (52.2%). 57.1% (12/21) achieved uMRD in both PB and BM, among which 6 of them (28.6%) achieved CR/CRi and 6 achieved PR (28.6%). All four patients with TP53 abnormalities achieved PR and two of them (50.0%) achieved uMRD in both PB and BM. One of 6 patients with del(11q) achieved CR (16.7%) and five achieved PR (83.3%), with 2 achieved uMRD in both PB and BM (33.3%). Among 13 assessable patients with unmutated IGHV, four of them achieved CR (30.8%) and nine achieved PR (69.2%), with 5 achieved uMRD in both PB and BM (38.5%). 18 patients had turned to ibrutinib maintenance with 12 of them finished 4th cycle of iFCR or 3 additional cycles of rituximab and could be assessed further. 10 of the patients achieved CR/CRi (83.3%) and 2 achieved PR (16.7%), with 8 achieved uMRD in both PB and BM (66.7%). The most common hematological toxicity events were neutropenia and thrombocytopenia and the non-hematological toxicity events were nausea and vomiting. The occurrence rate of grade 3 to 4 neutropenia and agranulocytic fever were 51.9% (15/29) and 17.2% (5/29) respectively. The most common ibrutinib-related AE were purpura, rash and diarrhea. The occurrence rate of AE induced discontinued ibrutinib more than 7 days, discontinued ibrutinib fewer than 7 days and ibrutinib decrement were 20.7%(6/29), 17.2%(5/29) and 20.7%(6/29) respectively. Conclusion: MRD-driven Ibrutinib plus FCR could achieve high response rate with uMRD in yonger fit patients with CLL/SLL, with manageable toxicity. Ibrutinib plus FCR could be one of the most promising choice as a time-limited regimen in the new drug era. Disclosures No relevant conflicts of interest to declare.

Interim Results of a Multicenter, Single-Arm Study to Assess Blinatumomab in Adult Patients (pts) with Minimal Residual Disease (MRD) of B-Precursor (BCP) Acute Lymphoblastic Leukemia (GMALL-MOLACT1-BLINA)

Interim Results of a Multicenter, Single-Arm Study to Assess Blinatumomab in Adult Patients (pts) with Minimal Residual Disease (MRD) of B-Precursor (BCP) Acute Lymphoblastic Leukemia (GMALL-MOLACT1-BLINA)

Clinical impact of early minimal residual disease detection at day 15 in precursor B-childhood acute lymphoblastic leukemia: an Egyptian experience

BackgroundChromosomal abnormalities in childhood acute lymphoblastic leukemia (ALL) are well-established prognostic markers and useful tools for minimal residual disease (MRD) assessment. This study aimed to stratify high-risk precursor B-childhood ALL (pre-B-ALL) patients according to standard prognostic factors (age and total leucocytic count), fluorescence in situ hybridization (FISH) analysis for these cytogenetic abnormalities [t (9;22) BCR/ABL, t(1;19)TCF3/PBX1, and 11q23 MLL gene rearrangement], and MRD status at day 15. Besides, we aimed to demonstrate the relation of these prognostic factors (standard and cytogenetic risk groups) to patients’ outcome at day 15 of induction therapy as well as exploring the impact of early MRD assessment during remission induction compared to other prognostic factors together with the ability to tailor investigations as needed especially in places with limited health resources without compromising the outcome. Seventy-two newly-diagnosed Egyptian children with pre-B-ALL, aged 6 months to 15.5 years, registered from February 2016 to February 2018 were included. They were treated according to the modified Children’s Oncology Group (COG) protocol. Patients were classified into (a) standard and high-risk groups according to standard prognostic factors. (b) Patients with the studied cytogenetic abnormalities and patients without the studied cytogenetic abnormalities. (c) Good outcome (negative MRD) and bad outcome (positive MRD) groups according to day 15 MRD status.ResultsThe studied cytogenetic abnormalities were identified in 22.2% of patients, all of them were in the high-risk group, and 75% of them had a bad outcome (positive MRD) at day 15 of induction therapy.ConclusionPatients with favorable presenting features (standard risk) and undetectable MRD after 2 weeks remission induction therapy would not be in need to advanced molecular studies, while these studies should be considered for patients with high-risk presenting features and high levels of MRD after 2 weeks remission induction therapy. Therefore, this could provide a cost-effective guideline in countries suffering from financial challenges without affecting the outcome

Upgraded Standardized Minimal Residual Disease Detection by Next-Generation Sequencing in Multiple Myeloma

Minimal residual disease (MRD) is one of the most powerful prognostic factors in multiple myeloma. Therefore, standardization and easy operation of MRD testing are crucial. Previously, we validated the sensitivity of 10-5 with spike in of plasmid controls for a standardized next-generation sequencing (NGS) approach based on triplicate measurements of bone marrow by LymphoTrack-MiSeq platform. To improve the technique, we replaced spike-in plasmid controls by genomic DNA from myeloma cells. A spike-in control of 0.001% was consistently detected in all 19 samples tested, confirming a uniform sensitivity of 10-5 of this upgraded protocol. MRD was detected in 14 of 19 patients (78%), with a significant (P=0.04) impact on progression-free survival based on high versus low MRD levels. Reproducibility of detection was confirmed by the extremely small interrun variation tested in three patients. In nine patients, MRD was tested in parallel by allele-specific oligonucleotide real-time quantitative PCR. NGS showed an improved sensitivity and provided quantification of MRD for cases assigned positive but not quantifiable by real-time quantitative PCR, obviating the need of patient-specific probes/primers. In summary, the use ofgenomic DNA as spike-in control simplifies NGS detection of MRD while preserving the sensitivity of 10-5. Validity and reproducibility of the standardized procedure were verified, and the prognostic impact of NGS-based MRD in myeloma was confirmed.

High CD38 expression in childhood T-cell acute lymphoblastic leukemia is not associated with prognosis.

Prognostic factors are not well exploited in childhood T-cell acute lymphoblastic leukemia (T-ALL). The aim of this study was to analyze the prognostic role of CD38 as well as minimal residual disease (MRD) and other biological factors in T-ALL. Immunophenotyping of bone marrow (BM) at diagnosis and MRD levels were determined using a standard panel of antibodies by 4-colour flow cytometry. A total of 96 children with T-ALL were enrolled. The results showed that 97.9% of T-ALL patients were positive for CD38 with a median level of 85.3%. CD38-high group had a worse early treatment response than the CD38-low group. However, CD38 levels were not associated with prognosis, albeit CD38-high group had a worse 5-year event free survival rate (55.1% vs. 66.6%, P> 0.05) and a higher 5-year cumulative incidence of relapse (35.6% vs. 19.8%, P> 0.05). Very high MRD levels (> 10%) were related to the worse survival. Neither flow cytometry based minimal residual disease (MRD) levels nor CD38 expression levels showed significant relation to the hazard of relapse (P> 0.05). We conclude that T-ALL has a high level of CD38 expression which is not associated with prognosis. Very high MRD level (> 10%) is related to the worse survival, however, FCM based MRD detection does not convey a significant prognostic value.

Poor Prognosis in Children with ABL-Class Fusion Positive B-Cell Acute Lymphoblastic Leukemia Treated According to AIEOP-BFM Protocols

ABL-class fusions other than BCR-ABL1 (or Ph+) are found in 2-3% of precursor B-cell acute lymphoblastic leukemia (pB-ALL) in children and adolescents. Occasional reports suggest that this rare ALL subtype has a poor prognosis and patients can benefit from treatment with tyrosine kinase inhibitors (TKIs). Aim of this retrospective study is to investigate the presenting features, treatment response and outcome in ABL-class fusion positive cases identified within large cohorts of patients treated in AIEOP-BFM ALL trials. This retrospective survey of ABL-class fusion positive pB-ALL other than Ph+ ALL was performed in patients aged 1-17 years at the diagnosis, treated from October 2000 to August 2018 according to the AIEOP-BFM (Associazione-Italiana- di- Ematologia-Oncologia Pediatrica-Berlin-Frankfurt-Münster) ALL 2000 and 2009 protocols in Austria, Australia, Czech Republic, Germany, Israel, Italy and Switzerland. While ABL-class fusions screening was not required by protocols, it was performed in some patients, according to centers' policies, usually after poor early treatment response. Overall, 46 ABL-class fusion positive cases with ABL1 fusions (N=15), ABL2 fusions (N=5), CSF1R fusions (N=3) and PDGFRB rearrangements (N=23) were identified. Compared with other pB-ALL children and adolescents, the ABL-class fusion positive cases presented with higher proportions of patients aged 10 years or older (52.2 vs. 22.2, P&amp;lt; .0001), hyperleukocytosis (WBC ≥100x109/l, 41.3 vs. 6.3, P&amp;lt; .0001), or poor minimal residual disease (MRD) response (&amp;gt;5x10-4 levels were observed in 65.2% vs. 18%, P&amp;lt; .0001 of patients after induction treatment phase IA and in 45.7% vs. 4.8%, P&amp;lt; .0001 after consolidation phase IB). For the entire cohort of 46 cases, the 5-year probability of event-free survival (EFS) was 49.1+8.9% and that of overall survival (OS) 69.6+7.8%; the cumulative incidence of relapse (CI) was 25.6+8.2% and treatment-related mortality 20.8+6.8%. Although not prescribed by the protocols, 13 patients received a TKI during different phases of treatment (TKI group), by choice of treating physicians, generally due to poor early treatment response. Eight TKI patients with high MRD levels at the end of induction phase IA received the TKI during consolidation phase IB, and six of them achieved either a low positive or negative MRD level at the end of consolidation phase IB. Nine of the 13 patients treated with TKIs underwent hematopoietic stem cell transplantation (HSCT) and only 1/9 (TKI+HSCT) relapsed. Thirty-three cases did not receive any TKI (no-TKI group) and eight of them relapsed; 6/17 patients treated with chemotherapy only, versus only 2/16 who underwent HSCT. Overall, 25 patients underwent HSCT, and of them 3 relapsed and 6 died of treatment-related complications. In patients with a WBC higher or lower than 100x109/L, the 5-year EFS was 36.8+12.7% vs. 59.9+11.6%, respectively (P= .21), and the 5-year OS was significantly lower in patients with a high WBC (48.8+12.9% vs. 87.4+6.8%, P= .036). This difference was more pronounced in the no-TKI group with a 5-year EFS 27.8+13.6% vs 61.8+12.7%, (P= .07), and an OS of 36.7+14.6% vs 94.4+5.4%, respectively (P= .0015). Presenting features, treatment response and outcome in this cohort of ABL-class fusion positive patients are markedly similar to those of patients with Ph+ ALL included in the EsPhALL studies. Our results suggest that TKIs and HSCT may be beneficial in reducing the risk of relapse. Thus there is an urgent need for large international cooperative controlled studies to investigate the impact of TKI, in combination with an appropriate chemotherapy backbone and the role of HSCT. To this purpose, an early identification of patients with ABL-class fusion positive acute lymphoblastic leukemia will be necessary. Disclosures Izraeli: sightdx: Consultancy; novartis: Honoraria; prime oncology: Speakers Bureau. Locatelli:Miltenyi: Honoraria; bluebird bio: Consultancy; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bellicum: Consultancy, Membership on an entity's Board of Directors or advisory committees. White:BMS: Honoraria, Research Funding; AMGEN: Honoraria, Speakers Bureau. Schrappe:Together with study group from SHIRE, JazzPharma, Servier, SigmaTau, Amgen, and Novartis.: Research Funding; SHIRE, Servier, and JazzPharma: Honoraria.

Long-Term Outcome of Relapsed Acute T-Lymphoblastic Leukemia (T-ALL) in Children and Adolescents

Introduction Despite improvements in first-line treatment of childhood T-ALL, relapse remains the main cause of treatment failure. Patients with T-ALL experiencing leukemia recurrence have a dismal outcome, mostly due to a failure to achieve a second complete remission (CR) or to subsequent relapse. Assessment of minimal residual disease (MRD) may allow identifying subsets of patients with different prognosis. We analyzed the outcomes of 141 Italian children and adolescents who experienced T-ALL relapse after frontline multicenter AIEOP-BFM ALL treatment trials. Methods: This retrospective study aimed at describing the outcomes of Italian patients with T-ALL who were enrolled in the AIEOP-BFM ALL2000, 2006 and 2009 trials and subsequently experienced disease relapse. Among the 750 T-ALL Italian patients enrolled in the above-mentioned trials, 141 had a disease recurrence (70/251 patients in ALL2000 trial, 29/190 in ALL2006 trial, and 42/309 in ALL2009 trial). Molecular MRD monitoring after induction therapy for leukemia relapse was available for 38 patients. Results: The 141 patients, 113 males and 28 females, had a median age of 9 years at diagnosis (range 1-17) and 10 at relapse (range 2-19). At diagnosis, 7 patients were allocated to the Standard (SR), 45 to the Medium (MR), and 89 to the High Risk (HR) group, respectively. Thirty-four (4 MR and 30 HR patients) of these children were given allogeneic hematopoietic stem cell transplantation (allo-HSCT) in 1st CR and 41 had received central nervous system (CNS) radiotherapy. Relapses were classified as very early (occurring &lt;18 months from diagnosis), early (occurring ≥18 months from diagnosis and &lt;6 months after completion of primary therapy), and late (occurring &gt;6 months after the end of the frontline protocol) in 92, 36, and 13 patients, respectively. Site of relapse was isolated bone marrow (BM) in 74 patients, combined BM/extramedullary (EM) in 23 patients, and isolated EM in 44 patients (involving a single EM site in 37 cases and &gt;1 EM site in 7 cases; CNS was involved in 29 patients). At the time of relapse, 7 patients were treated according to AIEOP ALL REC98 Trial, 57 according to AIEOP ALL REC2003 Trial, while the remaining 77 patients received other combination of chemotherapy. After reinduction/consolidation treatment, 58 patients were given allo-HSCT from either a matched family donor (16) or an unrelated donor (UD, 31 patients, of which 21 from a matched UD and 10 from a mismatched UD) or an HLA-partially matched relative (11). With a median follow-up of 7.5 years (range 2-14), 34 patients are currently alive; 17 of these patients had EM isolated relapse, which was very early in 13 cases, and 17 had BM involvement at relapse, with late relapse in 8 cases. The 8-year overall survival (OS) of the whole cohort was 23.3% (95% CI 16.5-30.7) (Figure 1A). Isolate EM relapse (Figure 1B) and late relapses were associated with a better OS probability. Both factors remained statistically significant in multivariable analysis. Moreover, in univariable analysis a better prognosis was observed in patients treated more recently (i.e., after year 2008) (8-year OS 31.8% vs 16.2%, p=0.01). After allo-HSCT, 29 patients are currently alive, while the remaining 29 patients died from progressive disease (21) or transplant-related causes (8), leading to a 8-year OS for patients given allo-HSCT in 2nd RC of 48.5% (95% CI 34.7-61.0). Of the 83 children given sole chemotherapy, 5 are currently alive, while the remaining 78 died due to progressive disease (53), organ-failure (7), infection (9), or other causes (9). MRD monitoring was performed for 38/97 patients with BM involvement (5 with late, 13 with early, and 20 with very early relapse, respectively). Patients with a post-induction MRD &lt;10-3 showed a reduced incidence of relapse (Figure 1C), resulting into better probability of 8-year OS (Figure 1D) in comparison to patients with higher MRD levels. Conclusions: Our results confirm that T-ALL relapse, especially if involving BM and occurring within 6 months from treatment discontinuation is still associated with poor prognosis, although in the last 10 years a higher proportion of children with relapsed T-ALL has been rescued by second line therapy, including transplantation. In this Italian retrospective cohort, a MRD value &gt;10-3 at the end of induction therapy predicts a miserable outcome, this finding allowing to identify patients eligible to experimental therapies. Figure 1 Disclosures Merli: Novartis: Honoraria; Amgen: Honoraria; Bellicum: Consultancy; Sobi: Consultancy. Rizzari:JazzPharma, Shire, medac , Sigma-Tau, Baxalta, Shire and Servier: Consultancy, Honoraria; Together with study group from Shire, medac , Sigma-Tau, Baxalta, Shire and Servier: Research Funding. Parasole:Servier: Honoraria; Baxalta: Honoraria; Eusapharma: Honoraria. Locatelli:bluebird bio: Consultancy; Miltenyi: Honoraria; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bellicum: Consultancy, Membership on an entity's Board of Directors or advisory committees.