Molecular Relapse-free Survival Research Articles

The SNP rs460089 in the gene promoter of the drug transporter OCTN1 has prognostic value for treatment-free remission in chronic myeloid leukemia patients treated with imatinib

Membrane transporters are important determinants of drug bioavailability. Their expression and activity affect the intracellular drug concentration in leukemic cells impacting response to therapy. Pharmacogenomics represents genetic markers that reflect allele arrangement of genes encoding drug transporters associated with treatment response. In previous work, we identified SNP rs460089 located in the promotor of SLC22A4 gene encoding imatinib transporter OCTN1 as influential on response of patients with chronic myeloid leukemia treated with imatinib. Patients with rs460089-GC pharmacogenotype had significantly superior response to first-line imatinib treatment compared to patients with rs460089-GG. This study investigated whether pharmacogenotypes of rs460089 are associated with sustainability of treatment-free remission (TFR) in patients from the EUROpean Stop Kinase Inhibitor (EURO-SKI) trial. In the learning sample, 176 patients showed a significantly higher 6-month probability of molecular relapse free survival (MRFS) in patients with GC genotype (73%, 95% CI: 60–82%) compared to patients with GG (51%, 95% CI: 41–61%). Also over time, patients with GC genotype had significantly higher MRFS probabilities compared with patients with GG (HR: 0.474, 95% CI: 0.280-0.802, p = 0.0054). Both results were validated with data on 93 patients from the Polish STOP imatinib study. In multiple regression models, in addition to the investigated genotype, duration of TKI therapy (EURO-SKI trial) and duration of deep molecular response (Polish study) were identified as independent prognostic factors. The SNP rs460089 was found as an independent predictor of TFR.

Ponatinib Improved the Prognosis of Philadelphia Chromosome-Positive Acute Lymphoblastic Leukemia: A Japanese Single-Center Cohort Study.

Introduction The overall survival (OS) of Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ALL) has improved with the combination of tyrosine kinase inhibitor (TKI) with intensive chemotherapy. In recent years, there has been increased interest in the possibility of long-term survival without allogeneic hematopoietic stem cell transplantation (HSCT) or maintenance therapy. The aim of this study was to determine the effectiveness of treatment and the resultant outcomes in Ph+ALL patients using real-world data. Methods We performed a single-center retrospective analysis utilizing Akita University Hospital data (Akita, Japan) from November 2000 to June 2023 to evaluatethe outcomes of TKI with intensive chemotherapy for Ph+ALL. Results Twenty-three patients with Ph+ALL were treated with intensive chemotherapy combined with TKI, including six imatinib, four dasatinib, and 13 ponatinib. The median patient age was 53 years (range; 28-67). Eighteen patients (78%) achieved complete molecular remission (CMR) within three months. HSCT was performed in 16 patients (70%), all of whom did not receive post-transplant TKI maintenance therapy. Six of the seven patients who did not undergo HSCT received maintenance therapy with ponatinib after intensive chemotherapy. The three-year OSwas 81%. Ponatinib treatment resulted in a much higher OS rate than imatinib/dasatinib (100% vs. 60%;P=0.011). CMR within three months was identified as a prognostic factor for molecular relapse-free survival (hazard ratio (HR)=0.22;P=0.027). CD20 positivity was identified as a risk factor for hematological relapse (HR=5.2, P=0.032). Conclusion Even in a single-center cohort study, ponatinib, as a combination TKI with intensive chemotherapy or maintenance therapy, may improve the prognosis of Ph+ALL. Patients with CMR within three months might not necessarily needto receive HSCT, but a subsequent treatment-free status could have been achieved only by HSCT. Furthermore, CD20 positivity may be a useful biomarker for future treatment decisions in patients with Ph+ALL.

Venetoclax–based low intensity therapy in molecular failure of NPM1-mutated AML

AbstractMolecular failure in NPM1-mutated acute myeloid leukemia (AML) inevitably progresses to frank relapse if untreated. Recently published small case series show that venetoclax combined with low-dose cytarabine or azacitidine can reduce or eliminate measurable residual disease (MRD). Here, we report on an international multicenter cohort of 79 patients treated for molecular failure with venetoclax combinations and report an overall molecular response (≥1-log reduction in MRD) in 66 patients (84%) and MRD negativity in 56 (71%). Eighteen of 79 patients (23%) required hospitalization, and no deaths were reported during treatment. Forty-one patients were bridged to allogeneic transplant with no further therapy, and 25 of 41 were MRD negative assessed by reverse transcription quantitative polymerase chain reaction before transplant. Overall survival (OS) for the whole cohort at 2 years was 67%, event-free survival (EFS) was 45%, and in responding patients, there was no difference in survival in those who received a transplant using time-dependent analysis. Presence of FLT3-ITD mutation was associated with a lower response rate (64 vs 91%; P < .01), worse OS (hazard ratio [HR], 2.50; 95% confidence interval [CI], 1.06-5.86; P = .036), and EFS (HR, 1.87; 95% CI, 1.06-3.28; P = .03). Eighteen of 35 patients who did not undergo transplant became MRD negative and stopped treatment after a median of 10 months, with 2-year molecular relapse free survival of 62% from the end of treatment. Venetoclax–based low intensive chemotherapy is a potentially effective treatment for molecular relapse in NPM1-mutated AML, either as a bridge to transplant or as definitive therapy.

Tyrosine Kinase Inhibitor Withdrawal Syndrome in Chronic Myeloid Leukemia Patients Participants of Two Discontinuation Clinical Trials

Discontinuation of tyrosine kinase inhibitors (TKI) is currently one of the main goals in CML treatment. One of the known adverse events after TKI discontinuation is withdrawal syndrome (WS), which can occur in about 30% of patients (pts), characterized by musculoskeletal pain that begins or worsens weeks after interruption and may be more severe in some cases, but rarely leading to the need for TKI reintroduction. Some studies suggest TKI dose reduction or optimization before stopping treatment may reduce WS rates. Aims: To estimate the incidence of WS after TKI discontinuation in CML in two clinical trials and to correlate the incidence of these events with patients' characteristics and molecular relapse-free survival (MRFS). Methods: We analyzed two cohorts of CML patients of two prospective, single-arm, phase II clinical trials: EDI-PIO (Clinicaltrials.gov: NCT02852486) and DES-CML (ReBEC UTN code : U1111-1252-7312). In both trials, inclusion criteria were CML in the chronic phase, treated with TKI for at least three years, and with deep molecular response (MR4.5) for two years. In the first trial, TKI was discontinued after using three months of pioglitazone, and in the DES-CML trial, after reducing the dose of the TKI by 50% for six months before discontinuation. TKI was reintroduced if the patient lost MR4.0 (EDI-PIO trial) or major molecular response (MMR) (DES-CML trial). Adverse events related to WS were evaluated until the fourth month after discontinuation. WS was defined as the onset of new musculoskeletal pain and/or an increase in pre-existing pain and/or the need to start any pain medication. The adverse event classification followed the Common Terminology Criteria (CTCAE- Version 4.0), musculoskeletal and connective tissue disorder. The data were collected and stored using the REDcap Platform (by Vanderbilt). MRFS was defined by discontinuation date until the last seen date or loss of MR4.0/MMR. The Kaplan-Meier method was applied for OS, whereas Log-Rank tests were applied to compare its curves. All statistical analysis were done by IBM-SPSS v. 24 and considered significant p-value &amp;lt; 5%. Results: Between September 2016 and April 2023, we analyzed 63 patients, 32 from the DES-CML study and 31 from the EDI-PIO trial. The median age at discontinuation was 58 years (24-79), 59% male, 52% Sokal low-risk, 35% intermediate, and 13% high; at discontinuation, 94% of the patients were using Imatinib, 3% Dasatinib, 1.5% Bosutinib and 1.5% Nilotinib. The median duration of TKI treatment until discontinuation was 10 years (3-20). Withdrawal syndrome occurred in 41% of cases and was more frequent in females (58% vs. 42%, P=0.02). Fourteen pts from the EDI-PIO study (45%) and 12 (37.5%) from DES-CML developed WS (P=0.61). According to CTCAE, the events were classified as grade 1, 36%, and 33%, while grade 2 was 57% and 58%; and grade 3 was 7% and 8% (P=0.90), respectively, in EDI-PIO and DES-CML trials. Symptoms started at month 1 in 20% of the patients and 73% in months 2 and 3. Seventeen (30%) pts used anti-inflammatory drugs, analgesics, steroids, or muscle relaxants (64% EDI-PIO vs. 66% DES-CML, P=0.90). There was no need to reintroduce TKI for treating WS. Molecular relapse free-survival (MRFS) at 12 months was 72% (95% CI 60-84%), with no difference by protocol (75% DES-CML, 70% EDI-PIO). MRFS at 12 months was 73% and 74% in the group with or without WS, respectively (P=NS). Conclusions: The incidence and severity of WS were similar in the two trials, corroborating data from the literature. WS was more frequent in females. The dose reduction did not reduce WS rates. However, this condition was self-limited and managed with drugs, without reintroducing TKI. There was no difference in MRFS between the groups with or without WS.

Long-Term Follow-up of the AST Trial of Treatment-Free Remission in Chronic Myeloid Leukemia Patients

Background: Treatment-free remission (TFR) is a new goal for chronic myeloid leukemia (CML) patients who achieved a long deep molecular response (DMR) with better quality of life, reduced adverse events and high economic impact. The primary objective of the AST trial was to estimate molecular relapse rate at 24 month in CP-CML patients who discontinued TKI. Secondary objective to explore predictive markers for sustained TFR through clinical and immunological analysis ( innate inmune response). This update provides longer follow-up data and includes a new cohort of patients. Patients and Methods: AST-Argentina Stop Trial (NCT05926128) is a multicenter prospective study that included patients from 15 centers. Recruited patients ≥ 18 years, treated with TKI for at least 4 years, sustained MR 4.0 for ≥ 2 years and confirmed typical BCR-ABL1 b3a2 and/or b2a2 transcripts. Molecular studies were centralized in 2 internationally standardized laboratories and were performed monthly during the first 6 months, every 2 months until the first year, and every 3 months during the second year. TKI was restarted due to loss of major molecular response (MMR). Expression of multiple NK cell immunophenotypic markers(CD3-CD56+) was analyzed by flow cytometry at discontinuation time and 3 months later. The nonparametric Mann-Whitney test was used to compare the differences between relapsed and responding patients. Molecular relapse-free survival was estimated using the Kaplan-Meier method and optimal cut-off points were obtained using ROC curves. Comparisons between survival curves were made using the Log rank test method. The differences were considered statistically significant with p-values less than 0.05. Multivariate analysis was performed using the COX regression model. Results: A total of 81 patients divided into 2 cohorts were evaluated: 46 patients recruited between February 2018 and July 2020 (1st cohort) and 35 patients recruited between July 2022 and April 2023. Between these two periods, recruitment was stopped due to the COVID19 pandemic. This analysis focuses on the 1st cohort that has completed 24 months in the study. The median age was 57.5 years (24-86), median duration of treatment before discontinuation was 10.5 years (4.2-20). TKI treatment prior to discontinuation was as follows: Imatinib in 34 (73%) patients, Dasatinib 8 (17%), and Nilotinib 4 (9%). According to Sokal risk score: 22 (48%) were low risk, 14 (30%) intermediate, and 10 (22%) high risk. Seventeen patients (37%) lost MMR, leading to a 63% molecular relapse-free survival rate with a median follow-up of 47 months (41-52). All patients who lost MMR recovered it after restarting the same TKI, with a median time to response of 2.8 months (1-7). With a prolonged follow-up, 2 late relapses were observed (18 and 42 months) (Fig 1). For a univariate analysis, the continuous variables were dichotomized seeking to maximize the difference between the different cohorts. The differences were significant in the variables time in DMR (cut-off point: 51 months, p=0.0166)(HR=0.97 (0.94 - 0.99); p=0.013). Two of the NK cell markers showed significant differences between groups at month 3 after starting treatment, PD1 (Mann-Whitney p=0.035; Log-Rank test p=0.033) and NK-p44 (Mann-Whitney p=0.015; Log -Rank test p=0.020). Multivariate analysis using the Cox model that included variables as gender, age at diagnosis, time in DMR, time in TKI prior to discontinuation, Sokal score, and type of inhibitor, the clinical predictor of time in DMR was the only predictor, significantly associated with a higher rate of TFR, (HR = 0.97 (0.95 - 0.99); p=0.020). No patient experienced disease progression to advanced stages or death for any reason. Conclusion:This is the first multicenter study of TKI discontinuation in CML patients in Argentina showing that TKI can be safely discontinued in those who achieve and maintain a DMR before discontinuation. Molecular relapse-free survival rate was slightly higher than that reported in the international literature, and longer follow-up confirmed the sustained response. DMR before discontinuation showed to be a robust predictor of TFR. Although the sample size was increased, longer follow-up is needed to validate these findings in the second cohort. Potential advantages of TFR will not only impact in patients' quality of life but also show considerable reduction in the use of economic resources.

Final Report: Somatic Mutations and HMGCLL1 Haplotype Are Not Associated with Molecular Relapse-Free Survival in Patients with Chronic Myeloid Leukemia Who Attempt Treatment-Free Remission

Background Chronic myeloid leukemia (CML) is a clonal hematopoietic stem cell disorder resulting from the BCR::ABL1 rearrangement. Patients with CML have a comparable life expectancy to that of age-matched individuals in the general population when they achieve an optimal response with tyrosine kinase inhibitor (TKI) therapy. With the aim of improving the quality of life of patients who are significantly affected by drug-related adverse events and financial burden, the practical goal of CML treatment has shifted to treatment-free remission (TFR), defined as the successful discontinuation (DISC) of TKI therapy without losing leukemia control. TKI treatment DISC is a safe procedure but requires appropriate candidate selection and frequent molecular monitoring. Several biomarkers were investigated, but no definite biomarker has yet been successfully identified and validated. We have investigated somatic mutations before TKI discontinuation and HMGCLL1 haplotype as a potential biomarker for TFR, given that they were previously described as predictors of CML outcomes. Patients and methods A total of 155 patients who attempted TKI discontinuation for TFR from 5 countries were included: Canada (n=71), Brazil (n=30), Argentina (n=28), Italy (n=23), and the Czech Republic (n=3). We applied our in-house single molecule-molecular inversion probe (smMIP) panel which is a barcoded error-corrected DNA-based sequencing with a limit of detection up to 0.2%. The panel encompasses 40 genes with 332 amplicon probes: epigenetic modifiers (n=7), activation signaling (n=12), myeloid transcription factor (TF; n=5), spliceosome (n=3), tumor suppressor (n=3), cohesion (n=4), miscellaneous (n=3) and 8 HMGCLL1 single nucleotide polymorphisms (SNPs). Two groups were constructed based on these eight SNPs: group 1: CTCAGGCA (C- haplotype) or group 2: ACGTAATG (A-haplotype). Samples were collected prior to TKI DISC when patients met the criteria for TFR attempt. Molecular relapse-free survival (mRFS) was calculated from the date of TKI DISC to the date of confirmed loss of deep molecular response (DMR). Loss of DMR includes single-time loss of major molecular response (MMR) or two consecutive episodes of loss of molecular response 4 log or deeper response (MR4). Kaplan-Meier survival estimate was used to evaluate mRFS and Cox's proportional hazard regression model was applied. Results The median MR4 duration prior to TKI DISC was 7.2 years (range 4.7-9.3), while overall TKI treatment duration was 8.5 years (range 6.0-11.6). With a median follow-up of 831 days (range: 460-1,415), out of the 155 patients, 68 (43.9%) lost response, among whom 6 lost MMR only, 12 lost MR4 only, and 50 lost MMR and MR4, both. Median time to MMR loss was 95 days (range 83.5-137). A total of 71 mutations were detected in 51 patients (32.9%). TET2 mutation was the most frequent mutation, detected in 17 cases (24%) followed by ASXL1 (n=14; 20%) and DNMT3A (n=12; 17%). When grouped by relevant biological pathways involved, mutations in epigenetic genes (n=42, 61%) were the most frequently involved. mRFS rate was 64% (95% CI [55.8-71.1%]) and 56% [48.2-64.0%] at 6 and 12 months, respectively. During the univariate analysis, no significant difference was observed in mRFS according to the presence, number, or type of somatic mutations, or the HMGCLL1 haplotype. Additionally, there were no significant differences in mRFS based on age, sex, Sokal risk group, line of TKI therapy, or TKI drug type prior to TKI DISC. However, MR4 duration prior to TKI DISC was associated with mRFS rate: patients with≥7.3 years (n=71) showed higher mRFS: 74.09% [62.05-82.82%] compared to those &amp;lt;7.3 years (n=74) with mRFS rate of 44.36% [32.54 -55.51] (p &amp;lt;0.01, HR 0.36 [0.21-0.63]). In addition, a longer duration of TKI treatment before TKI DISC was associated with higher mRFS: patients with ≥ 8.3 years of treatment (n=85) showed 71.8% mRFS [60.4-80.4], compared to 42.5% mRFS [30.5-54.0%] in those with &amp;lt;8.3 years (n=71) (p&amp;lt;0.01, HR 0.48 [0.31-0.74]). Multivariate analyses for mRFS confirmed that MR4 duration and the total duration of TKI treatment before TKI DISC were associated with TFR outcomes, but not the presence of epigenetic mutations, any mutation, or HMGCLL1 haplotype (Table1). Conclusion In CML, somatic mutations before attempting TFR are frequently observed. However, our current study does not support their prognostic significance as TFR-predictive biomarkers.

Long-term Results of Imatinib Discontinuation in Patients with Chronic Phase Chronic Myeloid Leukemia: National Multicenter Prospective Study.

The discovery of imatinib is a milestone for chronic myeloid leukemia (CML) (1). As life expectancy in CML patients has approached that of the general population (2), research has shifted towards improving quality of life and economic considerations. After 2010, it has been shown that some patients could maintain molecular response even after discontinuing imatinib (3). This national multicenter prospective cohort study aimed to observe the long-term consequences of discontinuing imatinib therapy in adult chronic phase CML patients. A total of 41 patients were included. The median follow-up time after imatinib discontinuation was 48 months (minimum-maximum 6-81 months). The rate of molecular relapse-free survival (MRFS) at 48 months was 33,2% (CI:48.2-18.2). Twenty-seven of 41 patients lost their major molecular response MMR, treatment was started again, and the molecular response was re-achieved with imatinib in all patients. There was no significant relationship between molecular relapse and clinical factors like duration of treatment or molecular response status. Discontinuing imatinib resulted in approximately 4,392,000 Turkish Liras (TRY) or 245,150 US dollars (USD) in savings. In conclusion, imatinib discontinuation with close molecular monitoring is a safe option and provides important national economic benefits and enhanced quality of life. This approach should be considered for all eligible patients. This is the first tyrosine kinase inhibitor discontinuation study from Turkey.

Long-term outcomes of frontline imatinib therapy for chronic myeloid leukemia in China.

Imatinib is the first-line therapy recommended for chronic myeloid leukemia (CML) patients in China. We reported a long-term follow-up study of patients on imatinib as first-line treatment for chronic phase (CP) CML to provide an important reference for the actual clinical treatment regimen of CML patients in China. We evaluated the long-term efficacy, safety, low-dose attempt after years of treatment, and treatment-free remission (TFR) of 237 CML-CP patients receiving first-line imatinib therapy. The median age was 46 years (interquartile range: 33-55). After a median follow-up of 6.5 years, the cumulative complete cytogenetic response, major molecular response (MMR), and MR4.5 rates were 82.6%, 80.4%, and 69.3%, respectively. The 10-year transformation-free, event-free, and failure-free survival rates were 97.3%, 87.2% and 53.5%, respectively. Fifty-two (21.9%) patients with sustained deep molecular response (DMR) were treated with low-dose imatinib after years of imatinib treatment. No significant differences in the 1-year and 2-year molecular relapse-free survival in MMR and MR4 were observed between the standard-dose and low-dose groups. Twenty-eight (11.8%) patients discontinued imatinib, and the median time to maintain DMR before discontinuation was 8.43 years. Thirteen patients (5.5%) remained in TFR for a median of 43.33 months. No patients transformed to accelerate or blast phase or died. No new, late toxicity was observed, and the most frequent grade 3/4 adverse events were neutropenia (9.3%), anemia (7.6%), thrombocytopenia (6.3%), and rash (4.2%). This study confirmed the long-term efficacy and safety of imatinib for treating Chinese CML patients. Additionally, it demonstrated the feasibility of imatinib dose reduction and TFR attempts in patients with sustained stable DMR after years of imatinib treatment in real-life settings.

Importance of TKI treatment duration in treatment-free remission of chronic myeloid leukemia: results of the D-FREE study

Treatment-free remission (TFR) is a new goal for patients with chronic myeloid leukemia in chronic phase (CML-CP) with a sustained deep molecular response (DMR) to treatment with tyrosine kinase inhibitors (TKIs). However, optimal conditions for successful TFR in patients treated with second-generation (2G)-TKIs are not fully defined. In this D-FREE study, treatment discontinuation was attempted in newly diagnosed CML-CP patients treated with the 2G-TKI dasatinib who achieved BCR-ABL1 levels of ≤ 0.0032% (MR4.5) on the international scale (BCR-ABL1IS) and maintained these levels for exactly 1 year. Of the 173 patients who received dasatinib induction therapy for up to 2 years, 123 completed and 60 (48.8%) reached MR 4.5. Among the first 21 patients who maintained MR4.5 for 1 year and discontinued dasatinib, 17 experienced molecular relapse defined as loss of major molecular response (BCR-ABL1IS > 0.1%) confirmed once, or loss of MR4 (BCR-ABL1IS > 0.01%) confirmed on 2 consecutive assessments. The estimated molecular relapse-free survival rate was 16.7% at 12 months. This study was prematurely terminated according to the protocol’s safety monitoring criteria. The conclusion was that sustained DMR for just 1 year is insufficient for TFR in CML-CP patients receiving dasatinib for less than a total of 3 years of treatment.

Effect of BCR::ABL1 transcript type and droplet digital polymerase chain reaction on successful treatment-free remission in chronic myeloid leukemia patients who discontinued tyrosine kinase inhibitor.

Droplet digital polymerase chain reaction (ddPCR) is an exact method of measurement. We conducted this study to identify the prognostic factors for successful treatment-free remission in patients with chronic-phase chronic myeloid leukemia who discontinued tyrosine kinase inhibitors (TKIs). We also aimed to validate ddPCR for predicting molecular relapse. This is a prospective, multicenter study. We enrolled patients treated with TKIs for at least 3 years with a confirmed sustained deep molecular response (DMR) for at least 1 year. TKI was re-administered in patients who experienced the loss of major molecular response (MMR). A total of 66 patients from five institutions in South Korea were enrolled. During a median follow-up period of 16.5 months, 29/66 (43.9%) patients experienced molecular relapse; the probability of molecular relapse-free survival (RFS) at 6 or 12 months after TKI discontinuation was 65.6% or 57.8%, respectively, with most molecular relapses occurring within the first 7 months. All patients who lost MMR were re-treated with TKI, and all re-achieved MMR at a median of 2.8 months. E14a2 transcript type (p = 0.005) and longer DMR duration (⩾48 months) prior to TKI discontinuation (p = 0.002) were associated with prolonged molecular RFS and with sustained DMR. Patients with both e13a2 transcript type and detectable BCR::ABL1 (⩾MR5.0) by ddPCR at the time of TKI discontinuation showed shorter duration of molecular RFS (p = 0.015). Our data suggest that transcript type and BCR::ABL1 transcript levels on ddPCR should be taken into consideration when deciding whether to discontinue TKI therapy.

Efficacy of Ropeginterferon Alpha 2b in Inducing Treatment Free Remission in Chronic Myeloid Leukemia - an International, Randomized Phase III Trial (ENDURE, CML-IX) of the German CML-Study Group

Background: Only a minority of chronic myeloid leukemia (CML) patients can eventually successfully discontinue tyrosine kinase inhibitor (TKI) therapy after achieving a stable deep molecular remission. Mechanisms underlying a durable treatment free remission (TFR) are not well understood but supposedly involve restoration of anti-CML immunity. It was therefore hypothesized that interferon alpha (IFN) - a potent inducer of Th1-immunity and prior standard therapy in CML - might improve the TFR probability. Randomized trials to improve TFR rates in CML are currently lacking. ENDURE, CML-IX (NCT03117816) is a multicenter, international phase III trial evaluating the role of a novel form of pegylated proline interferon-alpha 2b (ropeg-interferon-alpha, ropeg-IFN) in inducing TFR. Patients and Methods: CML patients in stable deep molecular remission (MR4 or better for at least 12 months prior to screening) and with history of at least 3 years of TKI exposure were eligible to participate in this study. Patients in stable molecular remission could also be included if they had failed a former TKI discontinuation attempt (2nd stopper). Patients were randomized 1:1 to receive either ropeg-IFN 100μg s.c. every 2 weeks for 15 months (ropeg-IFN arm) or no further treatment after TKI stop treatment (no treatment arm). The primary efficacy endpoint of the trial was molecular relapse free survival (MRFS) with molecular relapse being defined as loss of major molecular remission (MMR), which is any increase of the BCR::ABL1 transcript level to >0.1% according to the international scale (IS). Time to relapse is defined as the time from randomization to relapse. Secondary endpoints were MRFS at month 6, 12 and 24 after TKI discontinuation. BCR::ABL1 measurable residual disease (MRD) was monitored from peripheral blood and centrally assessed for all centers in Germany and locally at the French centers. There was a post study follow up to collect clinical and molecular data. Results: Between May 2017 and June 2021, 203 evaluable patients (68 female, 135 male) with a median age of 55 years were randomized at 24 centers in Germany and 3 centers in France to receive ropeg-IFN (n=95) or no treatment (n=108) after TKI stop. For 77 patients in the ropeg-IFN arm (81%) and 86 patients in the no treatment arms (80%) it was their first TKI discontinuation attempt. At the time of data cut off in June 2022, the median observation time for all patients was 36 months. The hazard ratio (HR) of molecular relapse for the ropeg-IFN cohort versus the no treatment cohort was 1.03 (95% CI, 0.68 to 0.1.55; log-rank P=0.89). The Kaplan-Meier probabilities of molecular relapse free survival (MRFS) by 6, 12, and 24 months after TKI discontinuation were 73% (95%-CI: 62-81%), 64% (95-CI: 53-73%) and 56% (95%-CI: 45-66%) for the ropeg-IFN versus 67% (95-CI: 57-75%), 60% (95-CI: 50-69%) and 59% (95%-CI: 49-68%) for no treatment (Figure 1). The MRFS at months 6 and 12 after TKI stop (secondary endpoints) were 70% (95%-CI: 60-79%) and 64% (95%-CI: 53-73%) in 91 patients for ropeg-IFN group versus 65% (95-CI: 56-74%) and 59% (95-CI: 49-68%) in 107 and 104 patients for the no treatment group. Of 90 patients who were candidates for restarting TKI due to MMR loss, 82 patients were actually evaluable for TKI restart. Of those, 77 patients re-achieved at least MMR within 12 months (median time to reestablishing MMR was three months). Of the 5 patients who did not regain MMR, one patient withdrew consent and others were treated for only 1, 3, 4, and 11 months after TKI restart. Ropeg-IFN was well tolerated. Hematological and non-hematological WHO grade 3/4 toxicity occurred in 23 patients in the ropeg-IFN (31 adverse events) and in 20 patients in the no treatment arm (26 adverse events). Three deaths were reported on study which were unrelated to CML (cardiac arrest, fall from stairs, unknown). A detailed safety analysis will be presented at the meeting. Conclusion: Ropeg-IFN maintenance after discontinuing TKI-monotherapy does not increase the proportion of patients, who persistently maintain at least an MMR. The German CML-V (TIGER) trial currently explores the impact of IFN maintenance on TFR when patients receive a combination of TKI plus IFN before TKI stop. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

The Prognostic Impact of HMGCLL1 Gene Variant on Treatment Outcomes in Chronic Myeloid Leukemia (CML) Patients: Adverse Impact on the Response, Failure, and Progression with Imatinib Which Can be Abrogated By the Use of 2nd Generation Tyrosine Kinase Inhibitor (TKI) Upfront Therapy

BackgroundHMGCLL1 is characterized as a lyase activity enzyme located in the extramitochondrial region. Its biological and physiological role is not fully elucidated. Our previous study (Leukemia 2019) demonstrated that: 1) The HMGCLL1 gene variant, ACGTAATG haplotype (A-haplotype) is associated with increased expression of overall levels and isoform 3 (IS3) of the HMGCLL1 gene and predicts a decreased likelihood of deep molecular response after Imatinib (IM) therapy, 2) blockade of HMGCLL1 IS3 results in G0/G1 cell cycle arrest, leading to increased eradication of CML cell lines and CML leukemic stem cells, 3) blockade of HMGCLL1 isoform 3 significantly suppressed CD34+ fractions in CML patients (pts). It was unclear whether a second-generation tyrosine kinase inhibitor (2G-TKI) can reverse the adverse impact of the HMGCLL1 gene variant in CML pts. The present study assessed the prognostic impact of the HMGCLL1 gene variant in CML pts treated with IM or 2G-TKI, and its impact on treatment-free remission (TFR) after TKI discontinuation. Patients and methods Samples from 387 pts were sequenced. Group 1 included 252 pts from 2 centers whose samples were archived retrospectively. These pts were treated with IM (n=190, 75.3%) or second-generation TKIs (n=62) including Dasatinib (n=15, 6.0%), Nilotinib (n=37, 14, 7%), and Bosutinib (n=10; 4.0%). Group 2 included 135 patient samples from 4 countries that attempted to discontinue TKI for TFR. We applied our internal CML-specific smMIP panel with 332 amplicon probes including 8 HMGCLL1 SNPs (rs10948926, rs10948927, rs9370435, rs4546489, rs4275061, rs9475323, rs9475327, rs9296791). Linkage disequilibrium (LD) was assessed using Haploview software (Bioinformatics 2005). For Group 1, treatment outcomes were evaluated concerning major molecular response (MMR), molecular response (MR) with 2 log/deeper (MR2) or 4 log/deeper (MR4), failure-free survival (FFS), progression, and overall survival (OS). Disease characteristics and treatment outcomes were evaluated and compared according to the HMGCLL1 variants using a dominant model. For Group 2, molecular relapse-free survival (RFS) was calculated from the date of TKI discontinuation to the date of confirmed loss of molecular response (either loss of major MMR or two consecutive episodes of MR loss). Kaplan-Meier survival estimate was used to evaluate RFS and Cox's proportional hazard regression model was applied using the dominant model. Results HMGCLL1genotype and haplotype As shown in Fig A, the LD plot showed no recombination among the 8 SNPs, leading to one block for the 8 SNPs to construct a haplotype. Two haplotypes were constructed as CTCAGGCA (C-) or ACGTAATG (A-haplotype) with MAF of 0.674:0.279 in Group 1, and 0.703:0.216 in Group 2, respectively. Summary of outcomes in table 1. Treatment outcomes following TKI therapy according to the HMGCLL1 haplotype Homozygous A-haplotype (A/A) was associated with worse outcomes, showing a lower MR2 (65.9% vs 78.9% at 12 months, p=0.012), lower MMR (64.4% vs 86.8% at 3 years, p=0.00029), lower MR4 (34.7% vs 62.3% at 5 years, p=0.0001; worse FFS (62.8% vs 77.3% at 3 years, p=0.0014), higher risk of progression (16.2% vs 3.4% at 5 years, p=0.000678), and worse OS (56.1% vs 77.7% at 10 years, p=0.0021). The adverse impact of A/A-haplotype was more prominent in the pts treated with Imatinib: A/A-haplotype pts showed a 30-50% lower chance of MR2, MMR, and MR4 achievement, and 2-3 times higher risk of TFR and progression in comparison to those having C-haplotype when treated with Imatinib. However, the use of 2G-TKIs could abrogate the adverse impact of the A/A-haplotype. Impact of HMGCLL1 variant on treatment-free remission following TKI discontinuation While the 12-month RFS rate was 59.9% in overall pts (n=135), an inferior 12-month RFS rate was noted in A/A haplotype (43.8% vs 62.3%) but with borderline significance (p=0.116). Conclusion: The present study demonstrated that the HMGCLL1 gene variant is confirmed as predictive of CML outcomes. Moreover, our result suggests that the adverse impact of the HMGCLL1 genotype can be abrogated by using 2G-TKIs as upfront therapy. We aim to validate this data in a larger cohort of pts treated with 2G-TKI therapy to reach a clearer conclusion on this result. HMGCLL1 genotype information would be helpful to guide CML therapy given that pts with adverse HMGCLL1 genotypes could benefit from 2G-TKI therapy as front-line therapy. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Risk Factor Analysis for Second Treatment-Free Remission Failure from the Canadian TKI Discontinuation (TRAD) Trial in CML Patients: Treatment-Free Remission Accomplished By Dasatinib

Background The Canadian TKI discontinuation (TRAD) trial (NCT02268370) has evaluated whether Dasatinib (DA) rechallenge can sustain a second treatment-free remission (TFR2) after failure of Imatinib (IM) discontinuation (DISC) for the first TFR (TFR1) attempt. We previously reported that: 1) The 12-month molecular relapse-free survival (mRFS) rate for TFR1 is 58.0%; 2) Re-challenge with DA following TFR1 failure after IM DISC restores deep molecular response (MR) quickly; 3) 12 months DA rechallenge does not significantly improve TFR2 rate (EHA 2022). The clinical risk factors associated with TRF2 failure are evaluated in this study. Patients and Methods This prospective study (BMS CA180-543, NCT#02268370) had 3 phases: 1) IM discontinuation for TFR1, 2) DA rechallenge, and 3) DA discontinuation for TFR2. Key inclusion criteria included: 1) CML in chronic phase, 2) minimum duration of IM therapy 3 years, 3) minimum duration of MR4.5 or deeper over 2 years. Molecular relapse was defined as an increase BCR::ABL qPCR >MR4 on 2 consecutive occasions, or a single increase in BCR::ABL qPCR >MR3. DA treatment was started at 100mg daily after molecular relapse was confirmed, and continued for at least 12 months after achieving ≥MR4 until TFR2 is attempted. Molecular relapse-free survival (RFS) after DA discontinuation was calculated and analyzed according to the risk factors. Results With a median follow-up duration of 27.5 months (range 1.8-51), in the TFR2 phase, 35 pts stopped DA for a TFR2. Only 3 of 35 pts (8.6%), maintained the MR at last follow-up, the remaining 32 lost the MR within a median 3.65 months. The actuarial mRFS rate at 6 and 12 months was 22.9% (95% CI, 10.8-37.6%) and 10.0% (2.7-23.1%). Potential risk factors for TFR2 from three different phases were evaluated, and 5 were found to be associated with TFR2 failure in univariate analysis (table 1): 1. In the DA rechallenge phase, failure to achieve MMR in less than 1 month with DA rechallenge increased the risk of TFR2 failure, in comparison to those who achieved MMR in less than a month (HR 4.656, p=0.0002). 2. Prior to DA DISC phase, any detectable BCR::ABL1 qPCR level between MR4 to MR5.4 showed an increased risk of TFR2 failure, compared to undetectable BCR::ABL1 qPCR level below MR5.5 (HR 4.04, p=0.0001). 3. Among the variables during the IM DISC phase: 4. Molecular relapse pattern: in comparison to the loss of MR4 only, those who lost MMR had an increased risk of TFR2 failure (HR 4.163, p= 0.001). 5. Time to loss of MR within 2.8 months after IM DISC increased the risk of TFR2 failure, in comparison who lost MR beyond 2.8 months (HR 4.717, p=0.0002). 6. Shorter doubling time (DT) at 2 months below 12.75 days and above 0 increased the risk of TFR2 failure, compared to DT at 2 months above 12.75 days or below 0 (HR 654, p=0.002) Multivariate analysis was performed to identify independent risk factors, identifying 3 clinical factors predictive of TFR2 failure: 1) Failure to achieve MMR in less than 1 month following DA rechallenge (p=0.007, HR 9.542 [1.819-50]); 2) DT below 12.75 days at 2 months after IM DISC (p=0.015, HR 4.368 [1.334-14.30]); and 3) any detectable BCR::ABL1 transcript level between MR4 and MR5.4 before DA DISC (p=0.047, HR 2.759 [1.014-7.513]). A risk score model was generated incorporating these 3 clinical risk factors. A score of 1 was assigned to each one of these risk factors. The group with a score of 0 vs 1-3 was labeled as low vs high-risk, respectively. The low-risk group (n=7) showed 85.7% and 34.3% of TFR2 rate at 6 and 12 months, while the high-risk group (n=24) showed 7.4% and 3.7% of TFR2 rate at 6 and 12 months, (p=0.0003; HR 6.518 [2.219-19.95] for high-risk group vs low risk; Figure 1). Conclusion As we have previously reported, DA treatment rarely achieves a sustained TFR2 after failing the first IM DISC attempt. However, our current result suggests that TFR2 attempt can be successful in a selected group of patients if: 1) Rapid reduction of initial molecular kinetics is achieved within 1 month of DA rechallenge, 2) an undetectable BCR::ABL1 qPCR level is reached before TFR2 attempt 3) longer doubling time at 2 months after IM DISC is noted. The proposed risk model can be used as a predictive tool for TFR2 failure. Further studies to improve TFR2 rate should investigate the addition of new therapies and consider the use of innovative tools with higher precision and sensitivity to quantify the MR. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Somatic Mutations Are Frequently Detected in CML Patients before Treatment-Free Remission (TFR) Attempt with Tyrosine Kinase Inhibitor (TKI) Discontinuation but with Uncertain Predictive Value for Tfr Failure

Treatment-free remission (TFR) has been accepted as a practical treatment goal in chronic myeloid leukemia (CML) patients. TFR is defined as successful discontinuation (DISC) of Tyrosine Kinase Inhibitor (TKI) therapy without losing leukemia control. Multiple clinical studies have reproduced a consistent TFR rate of about 50%. No definite biomarker has been identified or validated yet. Adnan et al (BCJ 2022) recently reported that epigenetic modifier gene mutations at initial diagnosis of CML are associated with TFR success after TKI DISC. The issue is the time gap between mutation profiling at initial diagnosis of CML and the clinical event of a TFR attempt, which is about 5-10 years. Mutation profiles in the samples obtained before TKI DISC have never been investigated as a TFR predictive marker. Next-generation sequencing (NGS) has been incorporated into clinical practice. Conventional targeted sequencing techniques have limitations such as the high error rate, its limit of detection is up to 2-5%. Mutation frequency and allele frequency (AF) were assumed to be very low in the patients who achieved deep molecular response. Thus, conventional NGS likely misses mutations with low AF. Single-molecule molecular inversion probe (smMIP) is a bar-coded, error-corrected NGS approach, can overcome the high error rate issue by tracking all sequence reads derived from a single strand. This study aims to detect somatic mutations using a smMIP panel to evaluate if the mutations assessed can be a biomarkers for TFR failure. Patients and Methods We applied our in-house CML-specific smMIP panel with a limit of detection up to 0.2%. The panel encompasses 37 genes with 332 amplicon probes: epigenetic modifiers (n=7), activation signaling (n=12), myeloid transcription factor (TF; n=5), spliceosome (n=3), tumor suppressor (n=3), cohesion (n=4) and miscellaneous (n=3). Our cohort included 135 patients who attempted TKI DISC for TFR from 4 countries: Argentina (n=28, 20.7%), Brazil (n=30, 22.2%), Czechia (n=3, 2.2%), Canada (n=34, 54.8%). Disease characteristics and outcomes were evaluated and compared according to the mutation profiles prior to TKI DISC. Molecular relapse-free survival (RFS) was calculated from the date of TKI DISC to the date of confirmed loss of molecular response. An episode of major molecular response (MMR) loss or two consecutive episodes of molecular response loss of 4 logs or deeper response (MR4) constituted molecular relapse. Kaplan-Meier survival estimate was used to evaluate RFS and Cox's proportional hazard regression model was applied. Results Median age was 55.5 years (25-72), 55% males, and Sokal Score risks rates were as follows: Low 51.8%, intermediate 26.8%, High 8.33%. All patients were in chronic phase at diagnosis. A total of 102 pts (78%) stopped Imatinib, while 24 pts (22%) stopped 2GTKI: Dasatinib (n=17) and Nilotinib (n=7). There was no difference in RFS between IM DISC vs. 2GTKI DISC: the patients who stopped IM showed RFS rate of 64.3% (40.9-80.4%) vs those who stopped 2GTKI showed 58% (48.5-67.7%; p=0.634). A total of 59 mutations were detected in 43 (31.9%) patients. TET2 was the most commonly mutated gene (n=15, 11.1%) followed by ASXL1 (n=10, 7.4%) and, DNMT3A (n=9, 6.7%). According to its biologic pathways of the mutation, mutations were detected in the Epigenetic modifiers (n=33, 56%) most frequently, followed by Cohesin (n=16, 27%), activated signaling (n=7, 12%), tumor suppressor (n=3, 5%) and splicing (n=1, 2%). According to the mutational profile before TKI DISC for the TFR attempt, no difference in RFS was observed according to the biological pathways of mutations or according to the presence of mutation (fig 1). Overall RFS at 1 year was 56% (95% CI [45.1-66.1%]) in patients without any mutations comparing to 67.5% (50.7-79.7%) in patients with mutation(s) (p=0.49; fig 2). The RFS rate at 1 year was 58.9% (48.3-68%) in patients with epigenetic mutations compared to 63.3% (43.6.-78.7%) in those without it (p=0.73). Even after adjustment for MR4 duration, we could not identify any predictive profile of RFS. Conclusion Somatic mutations were not infrequently detected in the patients qualified for TFR attempt using a technique detecting up to 0.2% VAF. Mutations in epigenetic genes were most frequently detected. However, it does not seem to have any predictive power for TFR success. Its biological relevance remains to be further investigated in future research. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Imatinib dose optimization based on therapeutic drug monitoring in Chinese patients with chronic-phase chronic myeloid leukemia.

Imatinib treatment often produces various adverse reactions in patients with chronic myeloid leukemia (CML), and increasing patients are pursuing dose optimization. In this study, the authors aimed to explore imatinib dose optimization based on therapeutic drug monitoring (TDM) in CML patients. The relationship between imatinib concentration and clinical response and adverse reactions was evaluated, then the dose-reduction data in 110 Chinese CML patients was also explored. Patients with a major molecular response (MMR) had higher imatinib plasma concentration compared with those not achieving MMR (1473.70±419.13 vs. 985.8±213.32ng/ml) when receiving 400mg daily. Imatinib concentration >1000ng/ml predicted improved event-free survival and failure-free survival. In addition, imatinib concentration was significantly correlated with leukopenia or neutropenia, diarrhea, edema, and rash. Patients receiving imatinib concentration >1685ng/ml were more susceptible to diarrhea and those with levels >1575ng/ml were more susceptible to periorbital and limb edema. Thirty-nine (35.5%) patients underwent low-dose therapy and seven (6.4%) patients received discontinuation therapy. Patients with a higher imatinib concentration were more likely to maintain MMR or deep molecular response after dose reduction. No significant difference in molecular relapse-free survival rate was observed between the low-dose and standard-dose groups over 1year and 2years. Furthermore, most adverse reactions significantly improved after dose reduction. Imatinib concentration was closely associated with clinical response and adverse reactions, suggesting that dose optimization based on TDM might achieve beneficial clinical outcomes. Dose reduction based on TDM is feasible and safe for patients exhibiting optimal response, which could improve adverse reactions.

P701: COVID-19 IN PATIENTS WITH CHRONIC MYELOID LEUKEMIA IN TREATMENT-FREE REMISSION: DISEASE SEVERITY AND IMPACT ON TFR STATUS

Background: Severe SARS-CoV-2 infections associated with high mortality rates are reported in a higher percentage of patients (pts) with hematologic malignancies compared to general population. In chronic myeloid leukemia (CML), pts with uncontrolled disease have a higher mortality risk. The impact of SARS-CoV-2 infection on CML pts in treatment-free remission (TFR) has not been studied so far. In particular, as immune control of residual disease may be important for TFR, the concern is that the infection could induce loss of TFR. Aims: To evaluate the outcome of SARS-CoV-2 infection in CML pts in TFR and assess any impact on maintenance of TFR. Methods: From March 2020 to December 2021, the CANDID study organized by the international CML Foundation has collected data on COVID-19 positive CML pts worldwide. Details on the registry were presented recently (Pagano ASH 2021). For this sub-analysis on pts in TFR additional information were collected including; molecular remission status (BCR::ABL1 ratios) before, during and after SARS-CoV-2 infection covering at least 6 months. For molecular analyses, BCR::ABL1 ratios were classified according to Cross et al (Leukemia 2015). In addition, ratios of 0% without indication of sensitivity were allocated as MR4 i.e. 0.01%IS. PCR outlier results were identified using the ROUT method by nonlinear regression with a maximum false discovery rate (FDR) of 1% (Motulsky et al 2006). Time to molecular relapse (MR) was measured from the date of COVID-19 diagnosis to the date of MR defined as loss of major molecular remission (MMR, BCR::ABL1 >0.1%IS) or the date of last molecular test. Molecular relapse-free survival (MRFS) and overall survival (OS) were estimated with the Kaplan-Meier method. The statistical difference between groups was performed using log-rank test. Results: By December 2021, 1050 COVID-19 positive CML pts were registered. 95 pts were in TFR at the time point of SARS-CoV-2 infection of which 89 (93.68%) recovered and 6 deceased (6.32%). Median age of TFR pts was 57 years, male were 51 (53.68%). Median time from CML diagnosis to reporting date was 13 years (range 3.7-27.0 years). TFR duration was 2.83 years in median (range 0.5 months – 10.1 years) including 19 pts with a duration < 1 year. From the 89 recovered TFR pts, 74 pts completed the 6-month follow up (83%), a further 6 pts with molecular follow-up of 3-5 months after COVID-19 diagnosis were still in TFR, 9 pts were lost to follow-up. Of 74 pts with complete reports, 69 pts remained in TFR (93%) and 5 pts lost TFR. For 71 pts, PCR results were obtained before, during and after infection. With the ROUT method 10 pts demonstrated outlier PCR tests, 61 pts demonstrated stable PCR results. There was no statistically significant difference in PCR results before and during/after infection (p>0.2). MRFS for these 71 pts 15 months after COVID-19 diagnosis was 86%. Probability of TFR loss was higher in pts with a TFR duration < 6 months compared to pts with TFR duration >6 months (27% vs 10%, Fig 1A). Additionally, there were no statistically differences in hospitalization rate (16% vs 23%, p=0.12) and severity of COVID-19 symptoms (12.6% vs 12%, p=0.87) comparing TFR and TKI treated pts. OS of COVID-19 positive TFR pts did not differ from COVID-19 positive pts on TKI therapy (HR 1.1, CI 0.47-2.54) (Fig 1B). Image:Summary/Conclusion: In this sub-analysis of the CANDID study, CML pts in TFR had similar severity and survival to CML pts who were on TKI therapy and there was no evidence of an increased risk of TFR loss after SARS-CoV-2 infection.

BCR–ABL1 transcript doubling time as a predictor for treatment‐free remission failure after imatinib discontinuation in chronic myeloid leukaemia in chronic phase

The doubling time (DT) of the BCR-ABL1 quantitative polymerase chain reaction (qPCR) transcript level reflects the re-growing fraction of leukaemic cells after discontinuation of tyrosine kinase inhibitor (TKI). The present study analyzed monthly DT within six months after imatinib discontinuation in 131 patients. Monthly DT was calculated as x = ln(2)/K, where x is the DT and K is the fold BCR-ABL1 change from the previous value divided by the number of days between each measurement. The optimal DT value was determined as 12·75 days at two months using a recursive partitioning method. The patients were stratified into three groups: the high-risk group (DT<12·75 days but >0, with rapidly proliferating chronic myeloid leukaemia (CML) cells; n = 26) showed the lowest molecular relapse-free survival (mRFS) of 7·7% at 12 months, compared to 53·6% in the intermediate-risk group (DT≥12·75 days, with slowly proliferating CML cells; n = 16) or 90·0% in the low-risk group (DT≤0, i.e., without proliferating CML cells; n = 71; P < 0·001). Monthly assessment of DT helps identify high-risk patients for treatment-free remission failure with an imminent risk of molecular recurrence, and to define low-risk patients who can be spared the frequent monitoring of monthly molecular tests.

Risk-adapted combined therapy with arsenic trioxide and all-trans-retinoic acid for de novo acute promyelocytic leuкaemia

Introduction. Non-chemotherapy for acute promyelocytic leukaemia (APL) with a combination of all-trans-retinoic acid (ATRA) and arsenic trioxide (ATO) provides for a high patient survival rate at lesser toxicity as effectively or superior to standard chemotherapy programmes.Aim — assessment of the ATO–ATRA risk-adapted exposure protocol in management of de novo acute promyelocytic leucaemia.Materials and methods. A prospective study included 51 primary APL patients aged 18–76 years. The program included remission induction (ATO 0.15 mg/kg intravenously, ATRA 45 mg/m2 orally) for 30–60 days in a low-risk (until remission) and 60 days — in a high-risk cohort that had idarubicin therapy added on days 2 and 4. Remission consolidation was attained with four (low-risk) or five (high-risk) courses. Minimal residual disease was monitored with real-time PCR at all phases.Results. The high-risk cohort was assigned 15 (29.4 %), the low-risk cohort — 36 (70.6 %) patients. Therapy induction till APL morphological remission was performed in 48/51 (94 %) patients. Molecular APL remission was achieved in 47 (92 %) patients, 100 % in the low-risk and 80 % in high-risk cohort. Early mortality was 6 % (n = 3), death in remission — 2 % (n = 1). Differentiation syndrome (DS) occurred in 16 (31.7 %) patients, more frequently in the high-risk vs. low-risk cohort (53.3 % and 22.2 %, respectively, p = 0.05; odds ratio 4.0 [1.1–14.4]). DS developed on days 1–20 (3 days median) of therapy. DS risk factors: a high-risk status, haemorrhagic syndrome and infection at the disease onset. A median follow-up time in survivors was 12.9 months (2.5–34.3), a six-month overall survival — 92 % (95 % CI: 85–100 %). A six-month overall survival was 100 and 73 % in the low- and high-risk cohorts, respectively (95 % CI: 54–100 %, p = 0.001). APL relapse not registered, 47 (92 %) patients survived and achieved the first molecular remission.Conclusion. A differentiated risk-adapted approach to APL therapy with cytostatic treatment added in high-risk patients only provided for a 100 % molecular remission and relapse-free survival. Therapy failures (early mortality and death in remission) affected high-risk patients due to a severe individual condition at the time of APL diagnosis.

Low Natural Killer (NK) Cell Counts and Functionality Are Associated With Molecular Relapse After Imatinib Discontinuation In Patients (pts) With Chronic Phase (CP)-Chronic Myeloid Leukemia (CML) With Undetectable BCR-ABL Transcripts For At Least 2 Years: Preliminary Results From Immunostim, On Behalf Of STIM Investigators

BackgroundIn pts with CP-CML, the notion that tyrosine kinase inhibitors (TKI) may never be stopped is currently challenged in the setting of clinical trials. In the pioneering French STIM trial, pts on imatinib for at least 3 years who had achieved and maintained undetectable BCR-ABL transcripts for at least 2 years had a 24-month molecular relapse-free survival of 39% with no relapses beyond 24 months. A low Sokal risk group and a long-lasting imatinib treatment were significantly associated with an increased freedom from molecular relapse but the role of other factors such as cellular immunity cannot be excluded. The aim of IMMUNOSTIM performed on a subset of 51 pts enrolled in the STIM trial was to analyze the potential implication of NK-cell and T-cell immunity in molecular relapse-free survival after imatinib discontinuation. MethodsPeripheral blood was drawn prior to and after imatinib cessation. All analyses were performed in a centralized fashion. Blood cell counts and differentials were determined using an automated blood cell count analyzer. Flow cytometry was performed on fresh cells to quantify CD56dim and CD56bright NK cells, CD3+ T cells, naïve and memory CD4+ and CD8+ T cells and CD4+ regulatory (CD25+CD127neg/low) T cells (TREGs). Expression of activating and inhibitory NK cell receptors was also analyzed. Functional analyses were performed using frozen mononuclear cells. The focus was put on NK cell function by means of a CD107a degranulation assay against the K562 cell line and an IFN-g secretion assay upon IL-12 and IL-18 stimulation. ResultsStudied pts' characteristics were comparable to that of the entire STIM study population. Median age was 63 years, 64.7% of pts were females and 52.9% has received prior IFN. Sokal risk group was low in 54.9%, intermediate in 35.3%, high in 7.8% and unknown in 2%. Median imatinib treatment duration was 57 months (36-94). Median follow-up after imatinib discontinuation was 42 months (24-54). A molecular relapse occurred in 28 pts after a median time off therapy of 2 months (1-20). Median BCR-ABL/ABL transcript ratio at relapse confirmation was 0.015% IS (0.006-1.546). Molecular relapse-free survival at 24 months was 47.1% (95% CI: 31.4-58.7). A significantly higher proportion of low low Sokal risk group and a trend toward longer imatinib treatment duration were found in pts who did not relapse compared to those who relapsed.At baseline, median leucocyte and lymphocyte counts were 4820/mm3 (2550-7860) and 1310/mm3 (720-2610), respectively and were comparable in pts who relapsed and those who did not. Median CD3+, CD4+, CD4+ TREGs, CD8+ T cells and CD4/CD8 ratio were 879/mm3 (315-1949), 534/mm3 (228-1248), 37/mm3 (4-94), 279/mm3 (72-998) and 2 (0.5-14.2), respectively, with no significant difference between pts who relapsed and those who did not. Analysis of CD4+ and CD8+ naïve, effector and central memory T cells did not reveal any differences between the 2 groups.In contrast, NK cell counts at imatinib cessation were significantly lower in pts who relapsed than in those who did not relapse (145/mm3 (67-450) versus 233/mm3 (70-727), p=0.0146). This decrease specifically affected the cytotoxic CD56dim population. NK cells numbers did not significantly increase in either group after imatinib discontinuation.NK receptor expression analysis did not show any significant defect in the expression of the activating NKG2D receptor and the CD94, NKG2A and KIR inhibitory receptors. However, the cytotoxic activity of CD56dim NK cells toward K562 and the IFN-g secretion potential of CD56bright NK cells upon IL-12 and IL-18 stimulation were significantly decreased when compared to those of healthy donors. Analyses are ongoing to further dissect NK cell function in pts who relapsed and those who did not. Updated results will be presented. ConclusionsOur stud shows a specific association between peripheral blood NK cells and clinical outcome after imatinib discontinuation in pts with long-lasting molecularly undetectable residual disease. These results suggest that NK cell-based immune surveillance may contribute to CML control after TKI cessation. Whether NK cells may be used as biomarkers among other factors to predict disease relapse after TKI cessation needs to be investigated. The understanding of NK cell defects may help in building strategies to restore an optimal NK cell-mediated anti-leukemic activity. Disclosures:Rea:BMS, Novartis, Pfizer, Ariad, Teva: Honoraria. Nicolini:Novartis, Ariad and Teva: Consultancy; Novartis & Bristol Myers Squibb: Research Funding; Novartis, BMS, Teva, Pfizer, Ariad: Honoraria; Novartis, BMS, Teva: Speakers Bureau; Novartis, Ariad, Teva, Pfizer: Membership on an entity's Board of Directors or advisory committees. Rousselot:BMS, Ariad, Pfizer: Honoraria from BMS, Ariad, Pfizer. Grants from BMS Other.

Long-Term Follow-up of the ALLG CML8 Twister Study of Treatment-Free Remission (TFR) in Patients with Chronic Myeloid Leukemia (CML)

Long-Term Follow-up of the ALLG CML8 Twister Study of Treatment-Free Remission (TFR) in Patients with Chronic Myeloid Leukemia (CML)