Success Of Treatment-free Remission Research Articles

High Level of CD8+PD-1+ Cells in Patients with Chronic Myeloid Leukemia Who Experienced Loss of MMR after Imatinib Discontinuation.

Treatment-free remission (TFR) is achieved in approximately half of chronic myeloid leukemia (CML) patients treated with tyrosine kinase inhibitors. The mechanisms responsible for TFR maintenance remain elusive. This study aimed to identify immune markers responsible for the control of residual CML cells early in the TFR (at 3 months), which may be the key to achieving long-term TFR and relapse-free survival (RFS) after discontinuation of imatinib. Our study included 63 CML patients after imatinib discontinuation, in whom comprehensive analysis of changes in the immune system was performed by flow cytometry, and changes in the BCR::ABL1 transcript levels were assessed by RQ-PCR and ddPCR. We demonstrated a significant increase in the percentage of CD8+PD-1+ cells in patients losing TFR. The level of CD8+PD-1+ cells is inversely related to the duration of treatment and incidence of deep molecular response (DMR) before discontinuation. Analysis of the ROC curve showed that the percentage of CD8+PD-1+ cells may be a significant factor in early molecular recurrence. Interestingly, at 3 months of TFR, patients with the e13a2 transcript had a significantly higher proportion of the PD-1-expressing immune cells compared to patients with the e14a2. Our results suggest the important involvement of CD8+PD-1+ cells in the success of TFR and may help in identifying a group of patients who could successfully discontinue imatinib.

The Success of Treatment Free Remission in Chronic Myeloid Leukaemia in Clinical Practice: A Single-Centre Retrospective Experience from South Africa.

Chronic myeloid leukaemia (CML) management has evolved from a disease once considered to be incurable just over 2 decades ago to that of one of a "functional cure" as defined by the sustained molecular response on stopping tyrosine kinase inhibitor(TKI) therapy. The next goal of CML management has been treatment-free remission (TFR). The past 4 years have seen much international data on TFR attempts in CML in clinical practice. However, Africa as a continent has lagged behind the rest of the world, in keeping up with the latest trends in CML management, and so this study aims to address this gap by assessing the outcome of TFR in CML in a single centre in South Africa (SA). We conducted a retrospective cohort study in 12 CML patients in the chronic phase to assess the success of TKI discontinuation. The patients were treated in King Edward VIII Hospital (KEH), a tertiary, academic hospital in KwaZulu-Natal, South Africa, and the study period was from June 2020 to May 2022. Patients included had to have been on TKI therapy for a minimum of 5 years and achieved a deep molecular response (DMR) for a minimum period of 3 years. The overall TFR cohort showed a success rate of 75% at a median follow-up of 12 months. All patients who failed TFR, defined as a loss of major molecular remission (MMR), failed within 6 months of stopping TKI therapy. All patients who failed TFR regained DMR after retreatment with TKI, with no disease progression reported. The only factor influencing the success of TFR was the total period of TKI therapy. Despite our study having a small cohort of patients, this study demonstrated that TFR in CML is an attainable goal, even in a resource-limited setting.

Asciminib in chronic myeloid leukemia: a STAMP for expedited delivery?

Asciminib is a novel tyrosine kinase inhibitor that specifically targets the myristoyl pocket. It has increased selectivity and potent activity against BCR-ABL1 and the mutants that most frequently prevent the activity of the ATP-binding competitive inhibitors. Results for clinical trials in patients with chronic myeloid leukemia that have received 2 or more tyrosine kinase inhibitors (randomized against bosutinib) or who have a T315I mutation (single arm study) have shown high levels of activity and a favorable toxicity profile. Its approval has offered new options for patients with these disease features. There are however a number of unanswered questions that remain to be defined including the optimal dose, understanding the mechanisms of resistance and, importantly, how it compares to ponatinib in these patient populations where we now have these two options available. Ultimately, a randomized trial is needed to answer questions to which we currently offer speculative informed guesses. The novelty of its mechanism of action and the exciting early data offers the potential for asciminib to address some of the remaining needs in the management of patients with chronic myeloid leukemia, including second line therapy after resistance to a frontline second generation tyrosine kinase inhibitors and improving in the success of treatment free remission. Multiple studies are ongoing in these areas and one can only hope that the desired randomized trial comparing to ponatinib will occur soon.

Modelling of immune response in chronic myeloid leukemia patients suggests potential for treatment reduction prior to cessation.

Discontinuation of tyrosine kinase inhibitor (TKI) treatment is emerging as the main therapy goal for Chronic Myeloid Leukemia (CML) patients. The DESTINY trial showed that TKI dose reduction prior to cessation can lead to an increased number of patients achieving sustained treatment free remission (TFR). However, there has been no systematic investigation to evaluate how dose reduction regimens can further improve the success of TKI stop trials. Here, we apply an established mathematical model of CML therapy to investigate different TKI dose reduction schemes prior to therapy cessation and evaluate them with respect to the total amount of drug used and the expected TFR success. Our systematic analysis confirms clinical findings that the overall time of TKI treatment is a major determinant of TFR success, while highlighting that lower dose TKI treatment for the same duration is equally sufficient for many patients. Our results further suggest that a stepwise dose reduction prior to TKI cessation can increase the success rate of TFR, while substantially reducing the amount of administered TKI. Our findings illustrate the potential of dose reduction schemes prior to treatment cessation and suggest corresponding and clinically testable strategies that are applicable to many CML patients.

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

Treatment-Free Remission in Chronic Phase Chronic Myeloid Leukemia Patients Treated with Nilotinib Front-Line, in Real-Life Conditions: Influence of Switching to Another TKI Prior to Cessation.

Nilotinib (NIL) as front-line therapy in newly diagnosed chronic phase (CP) CML patients (pts) is able to induce high rates of sustained deep molecular response and high possibilities of treatment-free remission (TFR). However, the identification of factors influencing successful TFR in this population remains imprecise. This observational study retrospectively analyzed TFR rates, outcome, and tried to identify factors related to successful TFR in in- and out-study 221 pts treated in this setting with NIL 600 mg, in "real-life" conditions. All pts with newly diagnosed adult CP-CML receiving NIL 300 mg BID alone front-line between 10/2007 and 06/2022, were eligible. Data were retrospectively collected according to the national regulations with pts' information. All pts were assessed and followed according to ELN recommendations 2006→2020 along treatment and to the recommendations of the Fi-LMC (D. Rea et al., Cancer 2018, i. e. 2 years of sustained MR4.5) in case of TFR. In this regard, a TKI was resumed if loss of MMR on one instance. BCR::ABL1 assessments were performed in the 2 reference laboratories, standardised, and expressed in % (IS) with ≥32,000 copies of ABL1 as control. The primary endpoints were the rate of successful TFR on NIL first-line. Secondary endpoints were the kinetics of molecular response, factors influencing outcome, survival, and safety of NIL. Two hundred and one patients were enrolled with 56% males with a median age at diagnosis of 50 (17.5-83) years, and 26% of them had cardiovascular risk factors at onset (tobacco abuse 10%, hypercholesterolemia 9.55%, diabetes 1.36%, none with history of cardiovascular events [CVE]). ELTS scores were high in 13%, intermediate in 30% and low in 53% of pts, unknown in 4% of pts. Twenty-six (12%) pts harboured additional chromosomal abnormalities (ACA) at diagnosis. The median follow-up after NIL initiation was 85.16 (5.72-174) months. After a median of 37.7 months, 119 pts (58%) were not on NIL anymore for toxicities, resistance or TFR. Sixty-eight (31%) pts obtained the TFR criteria and stopped NIL after a median of 66.7 (27-132) months. The median time between first MR4.5 datapoint and TFR was 39 (15.31-120) months. With a median follow-up of 20.3 (0.03-108) months after NIL cessation, the survival without MMR loss after NIL cessation (figure 1.) is 64.38% (95% CI: 53.35- 77.69). Interestingly, no CVE occurred after NIL cessation, as well as no blast crisis. Two patients died in TFR from competitive events (2 solid tumours). We went on comparing the TFR group vs the non-TFR group. The median age at TFR was 56 (30-87) years with no difference at CML diagnosis in terms of age (49 vs 50 years, p=0.096), ELTS (p=0.276), ACA (15% vs 11%, p=0.483) between the 2 groups. In contrast, there was a difference in favour of female vs male gender in the TFR group (56%) vs non-TFR group (39%, p=0.031), and the median time to reach MMR was shorter in the TFR group 5.04 vs 10.2 months, p<0.001; as well as the median time to reach MR4.5 in the TFR group 18.2 vs 36.1 months, p<0.001. We finally compared the successful vs the unsuccessful TFR pts requiring TKI-rechallenge, in univariate analysis and multivariate analyses. The univariate analysis identified pts that have switched to another TKI before TFR for whatever reasons was a risk factor for subsequent loss of MMR [HR: 3.09 (95% CI: 1.30-7.34), Cox p-value=0.011]. This was confirmed by the log-rank survival curves of TFR in patients with or without switch (figure 2., log-rank p=0.008). Surprisingly, neither the duration of NIL before TFR [HR: 0.98 (0.96-1.00), Cox p-value=0.072], nor the duration of MR4.5 prior to NIL cessation [HR: 0.98 (0.95-1.01), Cox p-value=0.15] were found to have an impact. Additionally, the prognostic scores did not influence TFR success on NIL. The multivariate analysis confirmed that switching to another TKI was an unfavourable risk factor for molecular relapse [HR: 2.87 (1.20-6.84), p-value=0.018], and that the lack of impact of the duration of MR4.5 [HR: 0.98 (0.95-1.01), Cox p-value=0.218] had no significant influence. NIL first-line is able to induce high rates of successful TFR in newly diagnosed CP CML patients and switching to another TKI for toxicity and/or resistance, prior to TFR, represents an unfavourable risk factor for the success of TKI cessation. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

S157: BCR::ABL1 DIGITAL PCR IDENTIFIES CHRONIC PHASE CML PATIENTS SUITABLE FOR AN EARLY TKI DISCONTINUATION ATTEMPT: A PATIENT-LEVEL META-ANALYSIS

Background: Digital PCR (D-PCR) is an emerging technique that delivers a highly accurate BCR::ABL1 quantification, even in CML patients with low residual disease. This is crucial in the context of treatment-free remission (TFR) for the selection of patients who may successfully discontinue TKI therapy. However, it is unclear how its prognostic value relates to time variables such as treatment duration prior to the TFR attempt. Current guidelines suggest aiming for a TKI treatment duration >6 years to increase TFR success rate. Aims: In current analysis, we aimed to assess the prognostic value of BCR::ABL D-PCR in relation to prior TKI treatment duration. Methods: We performed an Individual Patient Data Meta-Analysis (IPD-MA) combining data from different study cohorts in which BCR::ABL1 was assessed by D-PCR prior to TKI discontinuation. Eligibility criteria included age ≥18 years and CML diagnosed in chronic phase. Data of the participating studies were pooled and stratified based on D-PCR and/or treatment duration. BCR::ABL1 D-PCR was dichotomized based on each study-defined prediction cut-off. Strata were assessed for molecular relapse (MolR) with Kaplan-Meier estimates and with cox regression analysis including a frailty term for correction for between-study heterogeneity and including confounding variables: age at diagnosis, gender, Sokal score, TKI generation, treatment duration, DMR duration (model 1) and BCR::ABL1 transcript type (model 2). MolR was defined as a BCR::ABL1 >0,1%IS or a 1-log BCR::ABL1 increase in two consecutive analyses. Patients were censored at last follow-up. Results: For this meta-analysis, data were combined from five cohorts: four published cohorts (STIM2 cohort [Nicolini et al.], n=175; ISAV cohort [Diral et al.], n=107; Bernardi et al., n=111; Colafigli et al., n=50) and 1 unpublished cohort (Dutch cohort; n=40). The pooled dataset comprised 483 patients (Table). A total of 205 patients (42%) experienced MolR with a median time to relapse of 3 months. Median follow-up duration for TFR patients was 27 months. MolR patients had a significantly shorter treatment duration prior to TKI discontinuation (6,7 vs 7,9 years, p=0.006) and more often presented a BCR::ABL1 D-PCR above the study-defined prediction cut-off (34% vs 19%, p<0.001). Interestingly, the median treatment durations were almost identical in patients with a BCR::ABL1 below or above the cut-off (7.0 vs 7.5 years, p = 0.470). The probability of MolR at 24 months was 38% versus 58% for patients with a D-PCR BCR::ABL1 below versus above the prediction cut-off (p <0.001). In the cox regression analysis, the HR of D-PCR BCR::ABL1 below the cut-off for MolR was 0.48 (95% CI 0.35-0.66, p<0.001). Treatment duration and BCR::ABL1 transcript type also remained independent predictors, but TKI generation and DMR duration did not. When stratifying into 4 groups based on the D-PCR result and treatment duration, patients with a TKI treatment for ≥6 years and low D-PCR result had the lowest MolR rate (33% at 24 months, figure). Patients treated <6 years and with a low D-PCR result had a rate of 48% at 24 months, while patients treated <6 years and a D-PCR result above the cut-off had the highest MolR rate of 72% at 24 months. Image:Summary/Conclusion: These combined patient-level data of multiple CML cohorts further support the independent prognostic value of BCR-ABL1 D-PCR for TFR success rate. Importantly, patients with a TKI treatment duration <6 years and a low D-PCR result were found to have a clinically acceptable MolR rate (48%).

Highly Sensitive Droplet Digital PCR to Identify CML Patients with a High Probability of Achieving Treatment-Free Remission

Introduction: Treatment Free Remission (TFR) is the ultimate goal of therapy for most CML patients. Despite adopting consensus eligibility criteria of a sustained deep molecular response and more than 4 years of TKI therapy, the relapse rate after TKI cessation is still around 50%. More sensitive detection of residual leukaemia has the potential to improve our capacity to predict TFR outcomes for individual patients.Aim: To correlate droplet digital PCR (ddPCR) assay results with TFR outcome, especially in the setting of undetectable levels measured by qRT-PCR.Method: ddPCR was performed on blood samples from 51 TFR-eligible CML patients at the time of TKI cessation. 5 µg RNA per sample was used in 8 wells/sample using the BioRad QXDx BCR-ABL %IS kit on QX200 ddPCR system which yielded BCR-ABL1% (IS) directly. All these patients achieved MR4.5 that was sustained for ≥ 2 years.Results: 100% of patient were in MR4.5 via qRT-PCR at the time of stopping. 61% of the 51 patients evaluated relapsed within 12 months. Median duration of TKI therapy for the whole group was 5.8 years (range 2.2- 14 years). 20 patients achieved TFR success with a median follow up of 24 months (TFR group; sustained BCR-ABL1 <0.1% (IS) after TKI discontinuation for ≥12 months), while 31 patients relapsed (Relapse group; BCR-ABL1 >0.1% (IS) after stopping; median time of relapse 3 months, range 1-10 months).A ROC curve analysis correlated TFR outcome with ddPCR results, with BCR-ABL1 level ≥0.003% via ddPCR at the time of stopping identified as an optimal cut-off. Kaplan-Meier analysis showed that 89% of the patients with ddPCR ≥0.003 relapsed after TKI cessation, whereas the ddPCR <0.003 demonstrated a significantly reduced relapse rate to 54% (p=0.01, Figure 1A). In addition, the TFR group (median BCR-ABL1 0.00065%) demonstrated approximately two-fold lower levels of BCR-ABL1transcript level compared to the relapse group (median 0.0012%). Interestingly, 7/31 (23%) of the relapsed group had undetectable BCR-ABL1 transcript even with the current highly sensitive method, while this undetectable level was only observed in 35% of the TFR group.We next assessed other known predictors of TFR success relative to ddPCR results in a Cox proportional hazard model. We have previously demonstrated that the BCR-ABL1 halving time after commencing therapy is highly predictive of TFR. At a univariate level, transcript type (e13a2 versus e14a2, p=0.01), BCR-ABL1 halving time (p>0.0001), and mRNA quantitation by ddPCR ≥ 0.003% (p=0.02) were all significantly associated with clinical outcome. Other variables including gender, age, ELTS score, Sokal score, MR4.5 duration and TKI duration were not associated with clinical outcome in this cohort (Figure 1B). In the multivariate analyses (Figure 1C), ddPCR remained an independent predictor after adjusting for ELTS, TKI duration and MR4.5 duration. Interestingly, ddPCR was not an independent predictor after adjusting for BCR-ABL1 transcript type or halving time.Conclusion: QXDx ddPCR assay is a promising tool for molecular residual disease monitoring in CML, especially when the BCR-ABL1 is undetectable by conventional method. The CML patients with levels of detectable BCR-ABL1 ≥0.003% measured by ddPCR have a significantly higher probability of relapse compared to patients with lower levels of the transcript. The ≥0.003% BCR-ABL1 level cut-off value could be a potential tool to aid decision-making when attempting TKI discontinuation in CML. However, even though a measurable level of BCR-ABL1 above 0.003% via ddPCR identified patients at high risk of relapse after a TFR attempt, it does not rule out the possibility of TFR; and a negative ddPCR result does not exclude the risk of molecular relapse. ddPCR may be most useful where other TFR predictive factors including BCR-ABL1 transcript type and halving time are not available.In-kind support was received from Bio-Rad for this study. [Display omitted] DisclosuresBranford: Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Cepheid: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Qiagen: Honoraria, Membership on an entity's Board of Directors or advisory committees. Hughes: Novartis: Honoraria, Research Funding; Incyte: Honoraria; BMS: Honoraria, Research Funding. Yeung: BMS: Honoraria, Research Funding; Amgen: Honoraria; Novartis: Honoraria, Research Funding; Pfizer: Honoraria.

Treatment-Free Remissions in Newly Diagnosed CP CML Patients Treated with the Combination of Nilotinib + Pegylated Interferon Alpha 2a Versus Nilotinib Alone in the National Phase III Petals Trial

Treatment-Free Remissions in Newly Diagnosed CP CML Patients Treated with the Combination of Nilotinib + Pegylated Interferon Alpha 2a Versus Nilotinib Alone in the National Phase III Petals Trial

Treatment-Free Remission (TFR) after Two Different Durations of Nilotinib Consolidation in Patients with Chronic Myeloid Leukemia (CML) Previously Treated with Imatinib: Enestpath Study Results

Treatment-Free Remission (TFR) after Two Different Durations of Nilotinib Consolidation in Patients with Chronic Myeloid Leukemia (CML) Previously Treated with Imatinib: Enestpath Study Results

Cumulative Incidence of Treatment-Free Remission (TFR) for Patients with Chronic Myeloid Leukemia (CML): The Adelaide Experience

Background: For patients (pts) meeting specific clinical criteria, a trial of tyrosine kinase inhibitor (TKI) cessation is a safe option if regular quantitative RT-PCR (qRT-PCR) monitoring is performed and TKI is promptly recommenced in the event of molecular relapse [Mahon, Lancet Oncology 2010; Ross, Blood 2013]. With expert opinions incorporating TKI cessation into global guidelines such as the National Comprehensive Cancer Network and an increasing number of clinical trials demonstrating its success with both first and second-generation agents, treatment-free remission (TFR) is steadily being adopted into mainstream practice. Aim: To determine the proportion of pts becoming eligible and achieving a TFR attempt in a single academic centre. Patients and Methods: Adult pts receiving their primary CML management at the Royal Adelaide Hospital were included. We excluded pts referred specifically for clinical trials, transplantation, second opinions, and those with incomplete data. Clinical and molecular data from the period January 2008 to July 2017 were analysed. Specific TKI therapy was not mandated. Minimum criteria for qualifying for a TFR attempt were ≥3 years of TKI therapy and ≥2 years of sustained deep molecular response (DMR, BCR-ABL1 Results: A total of 245 pts were included in our analysis with a median follow-up of 6 yrs (0.2-19.2 yrs). Forty-seven pts will never qualify for TFR by our institution criteria due to death, allogeneic stem cell transplantation, loss to follow up, development of a T315I mutation and presence of atypical BCR-ABL1 transcripts. In total, 103 pts became eligible for a TFR attempt with an increasing proportion of pts becoming eligible for TFR with longer duration of TKI exposure (Table 1, Figure 1), from 16% at 4 yrs compared to 61% at 14 yrs. Eighty-two pts (80% of eligible pts) attempted TFR. The median age at TFR attempt was 61 yrs (range 34-89 yrs) and 55% (n=45) were male. The proportion of pts attempting TFR rose with longer duration of TKI exposure from 3% at 4 yrs compared with 53% at 14 yrs. The median duration of TKI treatment prior to TFR was 7.45 yrs (range 3-15.7 yrs) and the median duration of MR4.5 prior to TKI cessation was 2.8 yrs (range 2-9.9 yrs). The TKI at the time of the first TFR attempt in decreasing order of frequency was imatinib (n=53, 65%); nilotinib (n=18, 22%), dasatinib (n=10, 12%) and bosutinib (n=1, 1%). Durable TFR was achieved in 33 pts (40%) on the first attempt with a minimum follow-up of 12 months; 10 pts have Conclusion: TFR in published literature is achieved in 40-50% of cessation attempts for pts who meet the qualification criteria and these figures are in line with our real-world experience. Many pts (40%) ceased TKI outside of a clinical trial with close medical supervision and monthly PCR monitoring to ensure timely TKI recommencement if TFR failure occurred. Duration of TKI exposure correlated with TFR success which is comparative to recent data presented by the EUROSKI study. With longer follow-up, the availability of second generation TKIs for pts not achieving DMR on imatinib and the potential role of second and third attempts at TFR, we have observed a steady increase in eligibility for TFR, TFR attempts and durable TFR. Disclosures Shanmuganathan: Bristol-Myers Squibb: Honoraria, Other: Travel Support; Novartis: Honoraria, Other: Travel Support. Branford: Qiagen: Honoraria, Membership on an entity9s Board of Directors or advisory committees; Bristol-Myers Squibb: Honoraria; Ariad: Honoraria, Research Funding; Otsuka: Honoraria, Research Funding; Novartis: Honoraria, Membership on an entity9s Board of Directors or advisory committees, Research Funding, Speakers Bureau. Yeung: Novartis: Honoraria, Research Funding; BMS: Honoraria, Research Funding; Ariad: Honoraria, Research Funding. Yong: Novartis: Honoraria, Research Funding; Bristol-Myers Squibb: Honoraria, Research Funding; Celgene: Research Funding. Hughes: Novartis: Consultancy, Honoraria, Research Funding; BMS: Consultancy, Honoraria, Research Funding; Ariad: Consultancy, Honoraria, Research Funding.

Interim Results of the Canadian Tyrosine Kinase Inhibitor Discontinuation Trial for 2nd Attempt of Treatment Free Remission: Treatment Free Remission Accomplished By Dasatinib (TRAD)

Interim Results of the Canadian Tyrosine Kinase Inhibitor Discontinuation Trial for 2nd Attempt of Treatment Free Remission: Treatment Free Remission Accomplished By Dasatinib (TRAD)

Optimal Duration of Imatinib Treatment / Deep Molecular Response for Treatment-Free Remission after Imatinib Discontinuation from a Canadian Tyrosine Kinase Inhibitor Discontinuation Trial

Optimal Duration of Imatinib Treatment / Deep Molecular Response for Treatment-Free Remission after Imatinib Discontinuation from a Canadian Tyrosine Kinase Inhibitor Discontinuation Trial

Discontinuation of tyrosine kinase inhibitors in chronic myeloid leukemia: when and for whom?

Treatment discontinuation is considered one of the main goals of therapy for patients with chronic myeloid leukemia. Several criteria are felt to be necessary to consider discontinuation, while others may predict a better chance of achieving treatment-free remission. Criteria for discontinuation include patients in chronic phase chronic myeloid leukemia, a minimum duration of tyrosine kinase inhibitor therapy of 3 years, sustained deep molecular response for at least 2 years and a molecular response of at least MR4. In addition, proper education of the patient on the need for more frequent monitoring, possible side effects related to stopping and having a reliable real-time quantitative polymerase chain reaction laboratory are paramount to the safety and success of treatment-free remission. Realistically though, a maximum of only 20-30% of newly diagnosed patients will be able to achieve a successful treatment-free remission. In this article we will review for whom and when a trial of discontinuation should be considered.

Successful treatment-free remission in chronic myeloid leukaemia and its association with reduced immune suppressors and increased natural killer cells.

There is currently no biomarker that reliably predicts treatment-free remission (TFR) in chronic myeloid leukaemia (CML). We characterised effector and suppressor immune responses at the time of tyrosine kinase inhibitor (TKI) cessation in patients from the CML8 and CML10 clinical studies. Natural killer (NK) cells with increased expression of activating NK receptors were higher in patients who achieved TFR. There was no difference in the proportion of CD4+ or CD8+ T cells. Furthermore, we found that FoxP3+ regulatory T cells (T reg) and monocytic myeloid-derived suppressor cells (Mo-MDSCs) were concomitantly decreased in TFR patients, suggesting that the effector and suppressor arms of the immune system work in concert to mediate TFR. A discovery cohort (CML10) was used to generate a predictive model, using logistic regression. Patients classified into the high-risk group were more likely to relapse when compared with the low-risk group (HR 7·4, 95% CI 2·9-19·1). The model was successfully validated on the independent CML8 cohort (HR 8·3, 95% CI 2·2-31·3). Effective prediction of TFR success may be obtained with an effector-suppressor score, calculated using absolute NK cell, T reg, and Mo-MDSC counts, at TKI cessation, reflecting the contribution of both immune suppressors and effectors in the immunobiology underlying successful TFR.

Comprehensive Analysis of Hematological Parameter Changes after TKI Discontinuation for Treatment-Free Remission Attempt

Introduction: Tyrosine kinase inhibitor (TKI) therapy can result in the adverse events of prolonged anemia, thrombocytopenia and/or leukopenia via c-kit blockade in hematopoietic stem cells. Previous studies have reported that even low-grade adverse events could impair a patient's health-related quality of life. One of the benefits of TKI discontinuation is to allow patients to live drug-free, thereby preventing drug-related adverse events including cytopenias. The Canadian tyrosine kinase inhibitor (TKI) discontinuation trial has reported 59.1% and 21.5% molecular relapse-free survival (mRFS) rates after first and second attempts at treatment free remission (TFR) with imatinib (IM) or Dasatinib (DA) discontinuation, respectively. In the present study, we attempted to analyze the impact of TKI discontinuation on changes in hematological parameters, and its impact on TFR success after TKI discontinuation. Methods and materials: Throughout the trial, we have collected the hematoloigc parameters at 22 timepoints in 131 patients. These included Hb level, WBC count with differentials, and platelet count during IM discontinuation (7 times), DA rechallenge (10 times), and DA discontinuation (5 times). Results: With IM discontinuation, most of the hematological parameters showed a significant improvement within 3 months: Hb level rise by +10.47g/L (+8.86%; p=1.67x10-22), WBC count rise by +1.43x109/L (+30.08%; p=2.03x10-16), neutrophil rise by +0.99x109/L (36.76%; p=4.48x10-11), lymphocyte rise by +0.24x109/L (+20.64%; p=6.72x10-9), monocyte rise by +0.13x109/L (+35.9 0%; p=3.33x10-14), platelet count rise by +22.65 x109/L (+12.76%; p=1.03x10-7). Eosinophil counts were not significantly changed (p=0.475). With DA rechallenge, mixed changes were observed in hematologic parameters within 1 month: Hb level significant dropped by 11.57g/L (-8.26%; p=6.38x10-14) and platelet counts also showed a decreasing trend (-9.39x109/L or -4.57%; p=0.07), while significant increases were noted in lymphocyte (+0.41x109/L or +22.22%; p=0.00027), and monocyte counts (+0.14x109/L or +14.29%; p=0.001). No significant changes were noted in WBC counts (+0.32x109/L or +1.64%; p=0.234), neutrophil counts (-0.18x109/L or -10.42%; p=0.285), or eosinophil counts (+0.03 x109/L or 0%; p=0.185). With DA discontinuation, the Hb level rebounded by +7.08g/L within 3 months (+9.45%; p=0.0003). However, there was no significant change in the other parameters 3 months after DA discontinuation, including WBC (p=0.841), neutrophil (p=0.309), lymphocyte (p=0.995), monocyte (p=0.451), eosinophil (p=0.826) and platelet counts (p=0.533). When the changes in hematologic parameters were analyzed in correlation with mRFS, there was no association of those parameter changes with RFS after DA discontinuation. However, associations of mRFS following IM discontinuation were noted as follows: higher mRFS after IM discontinuation was observed in the group with a smaller change in Hb level (≤+1.17%, p=0.004), lymphocyte count (≤+1.06%; p=0.006), and monocyte count (≤+1.43%; 0.005) compared to those with a larger change. In other words, the group showing a rebounded Hb level after IM discontinuation showed a lower mRFS rate compared to those in whom the Hb did not rebound. A lower mRFS was noted in the group with a smaller change in neutrophil count (≤+1.07%) compared to those with a larger change (p=0.008), implying that the group with rebounded neutrophil count showed a higher mRFS compared to those not. Multivariate analysis confirmed: 1) IM treatment duration longer than 8.75 years is associated with a decrease in loss of molecular response by 13% per year (p=0.001, HR 0.871), 2) Hb level rebound above 22gm/L showed 2.8 times higher risk of molecular relapse (p=0.021, HR 2.801), 3) rebound rise of neutrophil count by 1.075% or above reduced the risk of molecular relapse by 52% (p=0.06, HR 0.485). Conclusion: Further research is warranted to explore the functional role of the hematopoietic stem cell fraction following prolonged TKI therapy in CML patients. Hematopoiesis in Ph-negative cell population could contribute to TFR after TKI discontinuation. Figure Disclosures Busque: ExCellThera: Patents &amp; Royalties; BMS: Consultancy; Novartis: Consultancy; Pfizer: Consultancy; Paladin: Consultancy. Savoie:BMS: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Pfizer: Consultancy. Keating:Celgene: Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria; Seattle Genetics: Consultancy; Janssen: Membership on an entity's Board of Directors or advisory committees; Shire: Membership on an entity's Board of Directors or advisory committees; Hoffman La Roche: Membership on an entity's Board of Directors or advisory committees; Sanofi: Membership on an entity's Board of Directors or advisory committees. Delage:Celgene: Honoraria, Research Funding; Novartis: Honoraria, Research Funding. Liew:Novartis: Consultancy, Honoraria. Leber:Jazz: Honoraria, Membership on an entity's Board of Directors or advisory committees; Alexion: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau.

The Interaction of Tumor Cells and Myeloid-Derived Suppressor Cells in Chronic Myelogenous Leukemia

Chronic myelogenous leukemia (CML) is a malignant myeloproliferative disease characterized by the formation of the BCR-ABL fusion gene. At present, basic studies of the pathogenesis of relapse after stopping tyrosine kinase inhibitors (TKIs) treatment have mainly concentrated on two main aspects: the leukemia stem cells (LSCs) and the tumor microenvironment. However, whether relapse or non-relapse patients who discontinued TKIs therapy, LSCs are still exist. Among a variety of factors that compose the CML microenvironment, myeloid-derived suppressor cells (MDSC) are considered to be a strong contributor to the immunosuppressive tumor microenvironment. Here, we designed the study to investigate the potential relation between tumor cells and MDSC in CML and find risk factors for relapse after discontinuation. We detected the percentage of MDSC and the BCR-ABL (IS) transcript levels in bone marrow of 50 CML patients in chronic phase at our center. The data indicated that the frequency of MDSC had significant positive correlation with BCR-ABL (IS) transcript levels (Figure 1A). In addition, the counts of MDSC had significant difference at different response stages (Figure 1B), especially the M-MDSC, a subtype of MDSC. The percentage of M-MDSC was significantly higher in patients with newly diagnosed or complete hematological response (CHR) or major molecular response (MMR) compared with those of CML patients obtained complete molecular response (CMR) (Figure 1C). When K562 cells or CD34+ cells were cocultured with M-MDSC at a 1:10 ratio, K562 cells or CD34+ cells proliferated significantly at day 3 (Figure 1D and E). K562 subcutaneous tumor formation in BALB/c node mice confirmed that tumors weight and volume of the coculture group were higher than control. Then, we further investigated whether tumor cells have an impact on MDSC through microvesicles (MV). After adding K562-MV to peripheral blood mononuclear cells (PBMCs) from healthy donors, MDSC counts appeared significantly elevated in the different K562 cells counts group compared to the control group (Figure 1F).To analyze the roles of K562-MV collected before and after TKIs discontinuation on MDSC, we established a TKIs discontinuation model using the K562 cell, which emulates the cessation of TKIs treatment of CML patients in some extent. The results showed that regardless of the Imatinib or Dasatinib treatment, a significant increase was observed in the proportion of MDSC after TKIs treatment cessation compared with the TKIs treatment groups (Figure 1G). Experiments in vivo also proved K562-MV after different treatments promoted the proliferation of MDSC (Figure 1H and I). In conclusion, our study introduces the notion of the role of MDSC as mediators in the cross talk between tumor cells and the microenvironment. MDSC would provide a novel and useful model to predict the relapse of CML by establishing a type of new risk stratification system. MDSC could be also act as a promising target in the relapse of CML. In addition, we found a mutual promotion of proliferation of tumor cells and MDSC, this bidirectional interaction results in a vicious cycle by providing a protective niche against immune attacks. Therapeutic interventions modulating this interaction might accelerate the success of treatment-free remission. Figure 1 Disclosures No relevant conflicts of interest to declare.

PF403 NEGATIVE MR4.0 CHRONIC MYELOID LEUKEMIA AND ITS IMPLICATIONS FOR TREATMENT‐FREE REMISSION

Background:In the last few years, several clinical discontinuation trials have demonstrated that 40–60% of chronic phase CML patients (CP‐CML) who have achieved a stable deep molecular response, can stop therapy without relapsing. However, there is no consensus as to whether or not the depth of the molecular response is a prognostic factor for treatment‐free remission (TFR), which is reflected in the discrepancy between the various guidelines and opinions of experts in the field regarding the optimal molecular response required, MR4.0 or MR4.5, for a TFR attempt.Aims:In this work, we hypothesize that a discrepancy in the classification of the level of molecular response between laboratories involved in clinical trials could introduce a bias in the evaluation of the prognostic impact of treatment‐free remission (TFR).Methods:In an attempt to clarify this issue, we stratified by molecular response a cohort of 1087 CML patients and compared our results with those of 200 patients enrolled in the EURO‐SKI trial.Results:We found that none of the patients classified as MR4.0 had detectable disease (0/169) (Figure 1A). In addition, the frequency of undetectable disease negative cases increased to 29% (61/211) and 65% (149/230) in the MR4.5 and MR5.0 groups, respectively (Figure 1A). By contrast, the frequency of MR4.0 with undetectable disease in the EURO‐SKI trial was 72% (49/68), decreasing to 56% (48/85) and 58% (25/43) in the MR4.5 and MR5.0 groups, respectively (Figure 1B).Summary/Conclusion:Our results suggest that (1) There may be a bias in patient stratification by molecular response in the EURO‐SKI trial, making it impractical to attempt any association between molecular response depth and TFR success, (2) we should reassess the current classification of MR4.0 to include only patients with detectable disease and (3) the minimum quality criteria for scoring molecular response when disease is undetectable should be raised, with samples with &lt;32000 ABL1 or &lt;77000 GUSB transcripts be considered as unevaluable for classification of DMR.image

The e13a2 BCR-ABL1 Transcript Is Associated with Higher Rates of Molecular Recurrence after Treatment-Free Remission Attempts: Retrospective Analysis of the Adelaide Cohort

The e13a2 BCR-ABL1 Transcript Is Associated with Higher Rates of Molecular Recurrence after Treatment-Free Remission Attempts: Retrospective Analysis of the Adelaide Cohort

Immune Effector Recovery in Chronic Myeloid Leukemia and Treatment-Free Remission.

Chronic myeloid leukemia (CML) is a hematological cancer, characterized by a reciprocal chromosomal translocation between chromosomes 9 and 22 [t(9;22)], producing the Bcr-Abl oncogene. Tyrosine kinase inhibitors (TKIs) represent the standard of care for CML patients and exert a dual mode of action: direct oncokinase inhibition and restoration of effector-mediated immune surveillance, which is rendered dysfunctional in CML patients at diagnosis, prior to TKI therapy. TKIs such as imatinib, and more potent second-generation nilotinib and dasatinib induce a high rate of deep molecular response (DMR, BCR-ABL1 ≤ 0.01%) in CML patients. As a result, the more recent goal of therapy in CML treatment is to induce a durable DMR as a prelude to successful treatment-free remission (TFR), which occurs in approximately half of all CML patients who cease TKI therapy. The lack of overt relapse in such patients has been attributed to immunological control of CML. In this review, we discuss an immunological timeline to successful TFR, focusing on the immunology of CML during TKI treatment; an initial period of immune suppression, limiting antitumor immune effector responses in newly diagnosed CML patients, linked to an expansion of immature myeloid-derived suppressor cells and regulatory T cells and aberrant expression of immune checkpoint signaling pathways, including programmed death-1/programmed death ligand-1. Commencement of TKI treatment is associated with immune system re-activation and restoration of effector-mediated [natural killer (NK) cell and T cell] immune surveillance in CML patients, albeit with differing frequencies in concert with differing levels of molecular response achieved on TKI. DMR is associated with maximal restoration of immune recovery in CML patients on TKI. Current data suggest a net balance between both the effector and suppressor arms of the immune system, at a minimum involving mature, cytotoxic CD56dim NK cells may be important in mediating TFR success. However, a major goal remains in CML to identify the most effective pathways to target to maximize an advantageous immune response and promote TFR success.