Discontinued Tyrosine Kinase Inhibitors Treatment Research Articles

Tyrosine Kinase Inhibitor (TKI) Discontinuation in Non-Allografted Ph+ Acute Lymphoblastic Leukemia Patients, a Campus ALL Real-Life Study

Introduction. Philadelphia-positive acute lymphoblastic leukemia (Ph+ ALL) patients are commonly treated with tyrosine kinase inhibitors (TKI) in combination with either steroids, chemotherapy and more recently also immunotherapy. In the past, allogeneic transplant (SCT) was considered the only curative option; however, with the introduction of more potent TKIs as well as immunotherapy this milestone is nowadays debated, mostly for patients who achieve a molecular response. Moreover, as in chronic myeloid leukemia (CML), it is becoming relevant to understand if patients may over time discontinue TKI treatment. For this purpose, it is pivotal to report the outcome of Ph+ ALL patients who, for any reason, stopped TKI treatment. Patients and Methods. Forty-seven adult Ph+ ALL patients treated since 1 January 2000, and who did not undergo a SCT, were retrospectively collected from 12 Italian centers participating to the Campus ALL network. Their treatment plan included a TKI +/- chemotherapy according to the center current practice and/or according to the ongoing national trial they were enrolled in. The median age was 63 years (20-84), 20 patients (43%) were males, 30 patients harbored a p190 transcript, 15 a p210 transcript and 2 had both transcripts. Twenty-six patients were treated within a trial, while 21 were off-protocol. For 32 patients, induction was based only on a TKI plus steroids, whereas the remaining 15 received a combination of a TKI plus chemotherapy (in 3 cases high intensity protocols such as the NILG (Northern Italian Leukemia Group) and HCVAD regimens, in 12 low dose chemotherapy). The reasons not to transplant patients were: donor unavailability (5), clinical decision, mainly due to age/unfitness (30), patient's refusal (4), and achievement of a molecular response (i.e. at least BCR-ABL/ABL ≤0.01%) (8). The median follow-up was 60 months, with a median overall survival (OS) not reached at the last follow-up and a median disease-free survival (DFS) of 12 years. At the last follow-up, 12/47 patients had experienced a relapse. At the end of the induction (i.e. after 3 months, at a median of +82 days, from treatment initiation), 27 patients had achieved a molecular response. Overall. a molecular response was obtained in 40/46 pts (data not available for 1 case) after a median of 5 month, and was associated with a significantly lower hazard of disease recurrence (HR=0.057, 95% CI: 0.006-0.51, p=0.011) after adjusting for gender, fusion protein, association with chemotherapy, CMR at 3 months. Results. TKI treatment was discontinued in 14 of the 47 patients evaluated. The reasons for discontinuation were either toxicity (6) or clinical/patient decision (8). Eight patients harbored a p190 transcript, 5 a p210 transcript and 1 carried both. At the time of discontinuation, the median age was 75 years (23-87) and patients had been on a TKI for a median of 57.5 months (8-160) prior to stopping treatment. For these cases, the median WBC at diagnosis were 8.6 x 10 9/l (2.1-306 x 10 9/l). In 7 patients the first TKI used was imatinib, in 3 dasatinib, in 3 ponatinib and in 1 nilotinib. All patients but 1 had achieved a molecular response before stopping treatment; the only patient who never achieved a molecular response prior to discontinuing the TKI had a rapid relapse (1 month). At the last follow-up, 9 cases were still in treatment-free remission (TFR), whereas 5 eventually relapsed after 1, 1, 4, 14 and 30 months, respectively. Re-challenge with a TKI led to a hematological and molecular response in 3 of the 5 patients. The remaining 2 patients, who had been previously heavily treated and whose TFR was of only 1 month, received salvage standard chemotherapy but eventually died from ALL progression. The median time of TFR for the entire cohort of 14 patients was 20.5 months (1-82). When considering only the 9 patients who remain off treatment, the median time of TFR was 29.5 months (7-82) (Table 1, Figure 1). Conclusions. We report the outcome of 14 Ph+ ALL patients who discontinued TKI treatment due to various reasons. Nine of them are still on TFR after more than 2 years at the last follow-up, reinforcing the concept that a TFR is feasible in selected adult Ph+ ALL patients. Of further relevance, TKI re-challenge was successful in 3/5 patients who relapsed, similarly to what observed in CML.

Biological Factors Associated with Treatment-Free Remission in Clinical Practice: Data from the Canarian Registry of CML

Introduction: The probability of maintaining treatment-free remission (TFR) after the discontinuation of tyrosine kinase inhibitors (TKI) is affected by clinical factors such as length of TKI treatment and the depth of molecular response. However, some individuals with similar treatment duration and response remain in TFR while others relapse. Thus, patient-specific factors must also play a role. Biological factors suggested to influence TFR include BCR::ABL1 transcript type, blasts at diagnosis, halving time (HT, first 3 months), BCR::ABL1 positivity at stop, and presence of somatic mutations. The aim of this study was to evaluate the biological factors associated with TFR in the clinical practice, using data from the Canarian CML Registry. Methods: The OMOP-standardized data of adult patients with chronic phase CML who discontinued TKI treatment included in the Canarian CML Registry (https://rclmc.es/rclmc/) were reviewed. Criteria to discontinue included TKI treatment ≥5 years and MR4.5 or better ≥3 years. TFR was defined as major molecular response (MMR), or deeper after stop. Molecular relapse was defined as loss of MMR in two consecutive tests. NGS was performed with the 30-gene panel Myeloid Solution (SOPHiA) on the MiSeq (Illumina) platform using 200 ng genomic DNA extracted from peripheral blood at diagnosis. Results: A total of 109 patients were included, with an average age of 50.5 years; 54 were male (49.5%). Median follow-up was 3.3 years. 86 patients discontinued from first-line, 21 from second- and 2 from third-line. 51% of patients (n=56) discontinued from imatinib, 31% from nilotinib (n=34), 16% from dasatinib (n=17), and 1% from bosutinib and ponatinib (1 patient each). The median TFR was 101 months ( Figure 1A; range 1.02-148.4 months). Thirty-two patients had molecular relapse and re-started TKI treatment: 36.7% with imatinib or dasatinib, 26.7% with nilotinib. Median time to regain MMR was 101 days (range 25-276). No difference was observed in the time to regain MMR for imatinib vs. 2G-TKI (106 vs. 144, p=0.419). No patients progressed to an accelerated phase. Differences were observed in duration of MR4 and MR4.5 prior to stop comparing the TFR vs. relapse groups (88.3 vs. 69.9 months, p=0.044; 74.2 vs. 58.6 months, p=0.079), but not total time on TKI (172.6 vs. 102.1, p=0.310), respectively. In terms of biological factors at diagnosis, 44 patients had blasts, 66.7% had a low Sokal risk. 23.9% expressed transcript e13a2 and 76.1% had e14a2. No differences in TFR were observed when blasts, Sokal or transcript were considered in chi-squared analyses. A long HT (>21.9 days, Shanmuganathan et al. Blood 2021;137) was of marginal significance for molecular relapse (p=0.076, OR 3.2) but no difference was found for short HT (<9.4 days). By Kaplan-Meier analysis, an MR3, 4, or 4.5 at stop was predictive of molecular relapse (n=42; Figure 1B) vs. an MR5 or undetectable (limit of detection 0.0001%). In multivariable analysis, only an MR5 or deeper at stop and withdrawal syndrome were predictive for TFR (p=0.003, HR 4.3; p=0.049, HR 0.20, respectively). NGS data was available for 47 patients. Myeloid mutations were detected in 21 patients (44.7%) at diagnosis, of these 11 had an epigenetic mutation (23.9%; in ASXL1, DNMT3A, TET2 or EZH2). 11 patients (23.9%) had a variant that was potentially germline (VAF 40-60%). By chi-squared and Kaplan-Meier analysis, no differences were observed between the median TFR for patients with or without a pathogenic somatic, epigenetic, ASXL1 or germline mutation. However, a greater separation of the curves was observed when considering TFR at 36 months for somatic (p=0.101) but not germline mutation. Conclusions: We confirmed previous observations that the biological factors BCR::ABL1 positivity at stop and longer HT were associated with molecular relapse although no difference was found for short HT. The impact of clinical factors on TFR, including duration of MR4 and MR4.5 prior to stop, were also confirmed in our real-life series with a long follow-up, while total TKI duration was not prognostic. Adnan Awad et al. associated the presence of epigenetic mutations at diagnosis with shorter TFR and higher relapse probability (Blood Cancer J. 2022;12). Here, a significant difference in TFR was not observed for epigenetic mutation at diagnosis; however, a tendency was observed between a pathogenic somatic but not a germline myeloid mutation and TFR at 36 months.

Mechanism of Late Recurrences of Chronic Myeloid Leukemia after Discontinuation of TKI Therapy: BCR::ABL1 Ins35bp Loss-of-Function Splicing Mutation and Regulatory T Cells

Introduction: Treatment-free remission (TFR) as one of the goals of treatment of BCR::ABL-positive chronic phase chronic myeloid leukemia (CML) has been proposed. Actually, approximately 40-60% of CML patients maintain TFR without recurrence after discontinuation of tyrosine kinase inhibitors (TKIs). In some of such patients, there are fluctuated cases in which BCR::ABL positive clones continue to be detected for long periods at levels of international scale (IS) BCR::ABL < 0.1%. Such fluctuated cases show no apparent molecular recurrence and maintain TFR for a long time, but they have also been shown to be more likely to eventually develop late recurrence (Haematologica 2022, Blood adv. 2020). We have reported that a higher percentage of PD-1 positive CD8 + T cells before and after TKI discontinuation is associated with molecular recurrence, and together with the possibility of assessing host immune response capacity after TKI discontinuation by using regulatory T (Treg) cells (Fujioka, et al. Cancers 2021). On the other hands, mutations in BCR::ABL caused by the alternative splicing, such as BCR::ABL Ins35bp, are known to be one of the TKI resistance in CML. Loss of BCR::ABL kinase activity is thought to result in loss of TKI sensitivity and thus failure to achieve deep molecular remission (Yuda, et al. Cancer Science 2017). In this study, we analyzed the mutations that cause splicing variants such as BCR::ABL Ins35bp and host immune response in CML patients to elucidate molecular mechanisms in the long-term maintenance of TFR and late recurrence. Methods: Twenty-four CML patients who discontinued TKI treatment for any reason at Akita University Hospital were included in the study. The trends of IS level after TKI discontinuation were monitored, and immune profile analysis by multi-color flow cytometry (FCM) was performed in all patients. Mutation analysis of the BCR::ABL region including splicing variants was performed in selected patients. Mutation analysis was performed on samples with sufficient cell count and IS > 0.0032% (MR 4.5), and the BCR::ABL region of these samples was amplified by long nested PCR and then analyzed by the next-generation sequencer (NGS). Results: First, BCR::ABL Ins35bp was evaluated by mutation analysis. Among CML patients who underwent mutation analysis, BCR::ABL Ins35bp was detected in all cases in which the samples could perform analysis at newly diagnosis (ND). Even after TKI discontinuation, a certain percentage of BCR::ABL Ins35bp was detected in all patients, and the percentage of BCR::ABL Ins35bp increased at the time of recurrence regardless of whether early or late. These results suggest that function-dead BCR::ABL Ins35bp clones may remain in CML patients with detectable BCR::ABL under and after TKI treatment, and eventually leading to recurrence with transcriptional promotion of native BCR::ABL. On the other hand, there were cases in which the BCR::ABL Ins35bp was lost at the time of recurrence. There is a possibility of immunological involvement in such cases. CML patients with detectable BCR::ABL in the TFR for a long time had a decreased immunosuppressive Treg cells, while analysis using late recurrence increased Treg cells prior to recurrence (figure). These suggest the presence of cases in which early recurrence is suppressed by host immune responses. Conclusion: Although the loss of function mutations such as BCR::ABL Ins35bp was previously thought to occur after TKI administration as a cause of TKI resistance, this analysis reveals that the clone is included from the ND before TKI treatment. Examining the BCR::ABL Ins35bp clone at ND may be possible to predict the possibility of recurrence after TFR. Host immune capacity, as assessed by the kinetics of Treg after TKI discontinuation, may contribute to prolonged TFR. Thus Treg monitoring may be important in predicting molecular recurrence, especially in BCR::ABL Ins35bp cases.

Long-Term Follow-up of Tyrosine Kinase Inhibitors Discontinuation in Chronic Myeloid Leukemia: A Single-Center Experience

Introduction: Ever since the availability of BCR-ABL1 tyrosine kinase inhibitors (TKIs) as treatment for chronic myeloid leukemia (CML), life expectancy of patients has dramatically improved, approaching that of the overall population. Several clinical trials have demonstrated the possibility of discontinuing TKI. However, the information on the safety of long-term TKI cessation is still limited. Methods: We carried out a descriptive, retrospective and single-center study, including 56 patients with CML who discontinued TKI treatment between January 2006 and July 2022. We defined strict molecular relapse as loss of MR4 (BCR-ABL1 International Scale (IS) ≤ 0,01% or undetectable BCR-ABL1 in samples with ≥10.000 transcripts), loose molecular relapse as loss of major molecular response (MMR) (BCR-ABL1 IS ≤ 0,1% in samples with ≥10.000 transcripts) and deep molecular response (DMR) as response greater than or equal to MR4. Progression-free survival (PFS) was estimated by the method of Kaplan-Meier and defined as the time from TKI discontinuation to the date of first event (loss of DMR or death). Results: We included 56 patients (table 1). Median age at time of stopping TKI treatment was 60,3 (50,7-75,8) years and 35 (62,5%) were male. 44 patients had received 1 line of TKI treatment, 7 two lines, 2 three lines and 3 four lines. The previous TKI treatment consisted of imatinib (n=34), nilotinib (n=6), dasatinib (n=34), two lines of imatinib because of pregnancy (n=1), imatinib dasatinib (n=3), imatinib nilotinib (n=1), dasatinib imatinib (n=1), dasatinib ponatinib (n=1), imatinib dasatinib nilotinib (n=1), nilotinib dasatinib nilotinib (n=1), imatinib dasatinib imatinib dasatinib (n=1), imatinib nilotinib dasatinib dasatinib+asciminib (n=1), imatinib nilotinib dasatinib nilotinib (n=1). Duration of imatinib treatment was 121,5 (100-172,8) months, dasatinib 74,4 (29-86,1), nilotinib 34,3 (19,1-45,6), ponatinib 49 and asciminib 20,7. The reasons for switching from first to second line were intolerance (n=7, 58,3%), resistance to any TKI (n=4, 33,3%) and pregnancy (n=1, 8,3%). From second to third line was intolerance (n=5, 100%). Duration of DMR before TKI discontinuation was 87,6 (49,2-116,4) months. The last molecular responses before TKI cessation were RM5 (n=18, 32,1%), RM4.5 (n=28, 50%), RM4 (n=9, 16%) y MMR (n=1, 1,8%). Reasons for TKI discontinuation were the presence of side effects (n=28, 50%), an attempt to achieve a treatment-free remission (TFR) in patients with a DMR (n=16, 28,6%), patient preference (n=10, 17,8%) and pregnancy (n=2, 3,6%). After TKI discontinuation, 34 (60,7%) patients have maintained DMR for a median of 4,22 (2,12-7,14) years, of which six more than 8 years being the maximum follow-up of 12,6 years. 5 patients had died while DMR due to CML-unrelated causes. The probability of PFS at 1 year and 12,6 years was 65,3% (95% CI: 58,6%-71,7%) and 34,8% (95% CI: 25%-44,1%) respectively (Figure 1). 22 (39,28%) patients had strict molecular relapse with a median of 3,9 (3,2-7,8) months, of which 12 (21,4%) were loose molecular relapses. Loss of DMR occurred most frequently in the first 6 months after TKI discontinuation (n=15, 68,1%). The last CMR loss was at 95 months. 18 patients restarted treatment, 2 died due to CML-unrelated causes, 1 maintained RMM without treatment due to intolerance and 1 stopped treatment due to personal preference. At the time of restarting treatment, the BCR-ABL1 IS was ≤10% (n=3), ≤1% (n=7), ≤0,1% (n=7) and ≤0,01% (n=1). After restarting treatment, 18 (100%) patients had MMR, of whom 16 (80%) had DMR. Median time to regaining DMR after resuming TKI therapy was 3 (0,9-3,05) months. A second attempt at TFR was made in 5 patients. The median duration of TKI therapy after restarting the treatment and the second discontinuation was 60,2 (40,2-63) months. 4 patients maintained CMR with a follow-up of 11 (7,2-24,4) months, and one patient died while DMR for reasons unrelated to CML. Adverse effects improved in most patients. TKI withdrawal syndrome was noticed in 12 (21,4%) patients. Conclusion: In our study, the PFS at 12,6 years was 34,8%. Including the patients who have had a second discontinuation of TKI, 39 (69,6%) patients remain in DMR off-treatment, with a median follow-up of 49,1 (26,7-85,7) months. 6 patients had a follow-up of more than 8 years without treatment, which is still ongoing. These data confirm the applicability and safety of TKI discontinuation. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

The prognostic role of NKG2A expression for patients with chronic myeloid leukemia after treatment discontinuation

This study aims to evaluate the possibility of tyrosine kinase inhibitors (TKIs) discontinuation in chronic myeloid leukemia (CML) patients who obtained sustained deep molecular response (DMR) and to explore the prognostic role of NK cells in treatment-free remission (TFR). Sixty CML patients who discontinued TKI treatment were enrolled, and we also investigated the immune profiles in 27 CML patients after TKI cessation. Of the 60 patients, the estimated TFR rate was 60.8% [95% CI: 49.5–74.8%] at 12 months. Patients who had longer TKI duration, major molecular response, and DMR maintenance time had a significantly higher TFR rate. And a higher percentage of NKG2A+NK cells and NKG2A+CD56brightCD16−NK cells were independent prognostic factors of TFR in multivariate analysis. These results indicate the practicality of the cessation of TKIs and patients with stable NK cell counts accompanied by higher cytotoxicity and increased killing capacity are more inclined to get sustained treatment-free survival.

CML-405: Treatment-Free Remission in Chronic Myeloid Leukemia: A Tunisian Experience

Context: Discontinuation of tyrosine kinase inhibitor (TKI) treatment for chronic phase (CP) chronic myeloid leukemia (CML) patients with a deep molecular response (DMR) has entered standard practice. Objective: In this study, we characterize the treatment-free remission in Tunisian CML patients. Design: This retrospective study collected data for CML patients who had discontinued TKI treatment as part of daily clinical practice in Sfax, Tunisia. Setting: Department of Medical Genetics in University Hospital. Patients or Other Participants: Patients with CML who discontinued their TKI were enrolled. Interventions: Quantitative assessment of the BCR-ABL transcript was performed using the Cepheid Xpert BCR-ABL ultra-assay. Main Outcome Measures: We investigated reasons for discontinuation, duration of TKI treatment before discontinuation, molecular response (MR) status at TKI discontinuation, and treatment-free remission (TFR) duration. Molecular recurrence is defined as the loss of major molecular response (MMR). Results: A total of 17 patients who discontinued treatment were enrolled in this study. Reasons for interruption were deep molecular response (n=13), adverse events (n = 1), and pregnancy (n = 3). TFR was maintained in 10 (64.7%) patients with a median follow-up of 26 months (8–127). The minimum treatment duration before discontinuation was 86 months. Five patients with sustained DMR (38.4%) had a molecular recurrence and re-initiated TKI. Conclusions: Our study highlights that TKI discontinuation was safe and effective in CML patients who are in sustained deep molecular response with longer TKI treatment duration. A larger study is mandatory for a comprehensive analysis of molecular recurrence in CML patients.

Observational Study of CML Italian Patients Who Discontinued TKIs

Abstract Background: Different studies analysed the outcome of patients (pts) who discontinued tyrosine kinase inhibitors (TKIs) reporting a median treatment-free remission (TFR) rate of 55%. On these bases it is judged safe to discontinue treatment in experimental contexts. Aims: Aim of our study was to evaluate TFR in the setting of Italian pts . Material and Methods: We designed a retrospective observational study of Italian pts with chronic phase CML who discontinued TKI treatment in deep molecular response (DMR). All Hematological Centers who are part of the GIMEMA group were invited to participate to this retrospective study and 32 centers had cases and participated to the study. Results: We collected a total of 293 pts. Median age was 59 years; 59%, 30% and 11% of pts were low, intermediate and high Sokal score respectively. 72% of pts were on treatment with imatinib, 28.% with either nilotinib (n=58), dasatinib (n=23) or bosutinib (n=1) at the time of discontinuation. 55% of pts discontinued in first line, 40% in second line, 5% in third line. Median duration of treatment with the last TKI was 77 months (mos, IQR 54;111) median time to deep molecular response (DMR, i.e. undetectable transcript or MR4/MR4.5/MR5) with the last TKI was 46 mos (IQR 30;73), median duration of DMR was 46 mos (IQR 31;74) before stop. Duration of treatment with TKIs and duration of DMR were shorter with 2nd gen TKIs than with imatinib (p Conclusion: Although our study has the limitation of a retrospective study, our experience within the Italian population confirms that discontinuation of imatinib and 2nd gen TKIs is feasible and safe in the clinical practice. Disclosures Fava: Incyte: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Novartis: Consultancy, Honoraria. Rege-Carmbrin: BMS: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Incyte: Consultancy, Honoraria. Rosti: Pfizer: Research Funding, Speakers Bureau; Bristol Myers Squibb: Research Funding, Speakers Bureau; Incyte: Research Funding, Speakers Bureau; Novartis: Research Funding, Speakers Bureau. Castagnetti: Novartis: Consultancy, Honoraria; Bristol Myers Squibb: Consultancy, Honoraria; Incyte: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria. Gugliotta: Incyte: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Bristol Myers Squibb: Consultancy, Honoraria. Gambacorti-Passerini: Pfizer: Consultancy, Honoraria, Research Funding; BMS: Consultancy. Abruzzese: Bristol Myers Squibb: Consultancy; Incyte: Consultancy; Novartis: Consultancy; Pfizer: Consultancy; ARIAD: Consultancy. Orlandi: Incyte: Speakers Bureau; Bristol-Myers Squibb: Speakers Bureau; Novartis: Speakers Bureau. Pregno: Incyte: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Novartis: Consultancy, Honoraria. Crugnola: Celgene: Honoraria; Novartis: Honoraria; BMS: Honoraria. Bocchia: Celgene: Other: Travel grant; Novartis: Other: Travel grant; Roche: Other: Travel grant; Jansen: Other: Travel grant. Galimberti: Bristol-Myers Squibb: Speakers Bureau; Novartis: Speakers Bureau; Incyte: Speakers Bureau; Pfizer: Speakers Bureau. Iurlo: Novartis: Consultancy, Honoraria; Bristol Myers Squibb: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria. Breccia: TEVA: Speakers Bureau. Cavazzini: Novartis: Consultancy; Incyte: Consultancy; Pfizer: Consultancy; Bristol-Meyers Squibb: Consultancy. Giai: Novartis: Consultancy, Honoraria; Incyte: Consultancy, Honoraria. Musto: BMS: Honoraria; Celgene: Honoraria; Novartis: Honoraria; janssen: Honoraria. Specchia: BMS: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Incyte: Consultancy, Honoraria. Pane: Novartis: Honoraria, Speakers Bureau. Baccarani: Incyte: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; BMS: Consultancy, Honoraria. Saglio: Roche: Consultancy, Honoraria; Incyte: Consultancy, Honoraria; Ariad: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Ariad: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Roche: Consultancy, Honoraria; Incyte: Consultancy, Honoraria; BMS: Consultancy, Honoraria; BMS: Consultancy, Honoraria.

Interferon-α may help prevent molecular relapse of chronic myeloid leukemia after the discontinuation of tyrosine kinase inhibitors.

Background:Currently, the goal of chronic myeloid leukemia (CML) treatment is normal survival and good quality of life without life-long treatment, namely, “treatment-free remission” (TFR). At present, approximately only 50% of patients with CML with a deep molecular response are able to discontinue tyrosine kinase inhibitor (TKI) without experiencing molecular relapse [MR; loss of major molecular response (MMR)]. In addition, prior interferon (IFN) treatment is associated with a higher rate of TFR.Methods:We aimed to evaluate the feasibility of TKI discontinuation in Chinese patients with CML and determine whether IFN could prevent MR when used after TKI discontinuation in patients with 0.0032% <BCR-ABLIS ⩽0.1%. Therefore, we retrospectively analyzed the data of patients with CML who discontinued TKI treatment at our center.Results:Forty-nine patients who discontinued TKI therapy after achieving MR 4.5 were included in this study, and the median follow-up time from TKI discontinuation was 27 (7, 75) months. Nineteen patients eventually lost MMR, and the TFR rate of the 49 patients was 67% (95% confidence interval 53.6%, 80.3%) at 12 months. The duration of MR 4.5 ⩾54 months and duration of imatinib ⩾85 months were significantly associated with a higher TFR rate. Of the 22 patients with 0.0032% <BCR-ABLIS ⩽0.1%, 12 received IFN-α treatment. The median IFN-α therapy duration was nine (2, 18) months, and three patients eventually lost MMR. Three patients discontinued IFN-α after 2, 2.5, and 10 months, and maintained MMR for 9, 8, and 11 months after IFN discontinuation, respectively. Of the 10 patients not receiving IFN-α treatment, eight eventually lost MMR. The MR-free survival rate was significantly different between the patients treated with and those treated without IFN-α over 24 months (70.7% versus 15.0%, p = 0.002).Conclusion:These results indicate that after TKI discontinuation, IFN-α can be administered to patients with 0.0032% <BCR-ABLIS ⩽0.1%, which may help prevent MR.

Pregnancy outcomes of women whom spouse fathered children after tyrosine kinase inhibitor therapy for chronic myeloid leukemia: A systematic review.

The introduction of tyrosine kinase inhibitors (TKIs) has revolutionized the therapy of chronic myeloid leukemia (CML). Although the efficacy of TKIs is beyond dispute, conception-related safety issues are still waiting to be explored, particularly in males. This systematic review aimed to summarize all available evidence on pregnancy outcomes of female spouses of male CML patients who fathered children after TKI treatment for CML. We performed a systematic search in seven electronic databases for studies that reported on male CML patients who did or did not discontinue TKI treatment before conceiving, and the pregnancy outcomes of their female spouse are available. The search centered on the TKI era (from 2001 onward) without any other language or study design restrictions. Out of a total of 38 potentially eligible papers, 27 non-overlapping study cohorts were analyzed. All were descriptive studies (case or case series studies). Altogether, 428 pregnancies from 374 fathers conceived without treatment discontinuation, 400 of which (93.5%) ended up in a live birth. A total of ten offspring with a malformation (2.5%) were reported: six with imatinib (of 313 live births, 1.9%), two with nilotinib (of 26 live births, 7.7%), one with dasatinib (of 43 live births, 2.3%), and none with bosutinib (of 12 live births). Data on CML status were scarcely reported. Only nine pregnancies (from nine males) and no malformation were reported in males who discontinued TKI treatment before conception. Malformations affected, on average 2.5% of live births from fathers who did not discontinue TKI treatment before conception, which is comparable with the rate of malformations in the general population. Large-scale studies with representative samples are awaited to confirm our results.

PB1941 PATIENT REPORTED OUTCOMES (PROS) SHOW SUPERIOR QUALITY OF LIFE (QOL) FOR CHRONIC MYELOID LEUKEMIA (CML) PATIENTS TREATED WITH FIRST COMPARED TO NEWER GENERATIONS OF TYROSINE KINASE INHIBITORS (TKIS)

Background:Tyrosine kinase inhibitors (TKIs) have prolonged the survival of patients with chronic myeloid leukemia (CML). Nowadays, the life expectancy of these patients is approaching that of an age‐matched population. Since Imatinib, a first generation TKI, was first introduced 20 years ago, several newer more potent TKIs, have been approved for CML treatment. While these drugs are effective in treating CML, they come with the trade‐off of adverse effects. Some are common to all and some are drug‐specific. As most patients will receive lifelong treatment, quality of life (QOL) is becoming a major concern. Yet, QOL under treatment with these drugs has not been directly compared. In this study, we assessed the QOL and symptom burden in a cohort of patients with CML, using a patient reported outcomes (PROs) questionnaire.Aims:To compare QOL and symptom burden in patients with chronic phase (CP) CML treated with first generation compared to the newer generation TKIs.Methods:This is a nationwide study of patients with CP‐CML who were treated with TKIs. This study was initiated in collaboration with the Israeli CML Patients Organization. Study participants completed the validated European Organization for Research and Treatment of Cacner (EORTC) 30 items questionnaire (core30)and a supplementary EORTC 24 items CML‐specific questionnaire. Additional QOL items were added by the researchers and in addition demographics and treatment related information were documented. validated scales were used for evaluation. T‐test was used to compare the scales. We used the Mann‐Whitney test to compare medians and χ2 to compare categorical variables.Results:Overall, 129 patients completed the questionnaire. The median age of these patients was 56 (range: 25 to 89) years and 67 (60%) were males. Patients were treated with first generation TKIs [original imatinib (Gleevec®) (n = 21, 16%) or imatinib‐Teva (n = 25, 19%)] and second or third generation TKIs [dasatinib (n = 22, 17%), nilotinib (n = 17, 13%), bosutinib (n = 2, 1.5%) or ponatinib (n = 2, 1.5%)]. 22 patients (17%) discontinued TKI treatment. The median duration of treatment free remission (TFR) in patients who discontinued TKIs was 13 (range: 1 ‐ 59) months.The median age of patients who received first generation TKI was 67 (range: 32 ‐ 89) years, and 45 years (range: 25 ‐ 82) of patients treated with second or third generation TKIs (P &lt; 0.0001). Patients on first generation TKIs expressed significantly more satisfaction from their quality of life during the preceding week (P = 0.006) and during the preceding 3 months (P = 0.001). Patients on first generation TKIs also reported lesser limitations in daily (P = 0.02) and social (P = 0.02) activities in the preceding week and also expressed a lesser degree of negative emotions such as anxiety or depression (P = 0.006). In patients treated with first generation TKIs the symptoms’ burden was significantly lower. For example, patients reported of less fatigue (P = 0.0021), less pain (P = 0.004), less dyspnea (P = 0.029) or constipation (P = 0.038), lesser degree of impaired body image (P = 0.01) and even less financial burden (P = 0.005) during the preceding week if they were treated with first generation TKIs. In a linear regression model, only the type of drug (first generation vs. newer generations) predicted global QOL (P = 0.006) whereas age and gender did not.Summary/Conclusion:The reported QOL of patients with CP‐CML who receive first generation TKI is superior to that of patients receiving newer generation TKIs.

Feasibility of Treatment Discontinuation in Chronic Myeloid Leukemia in Clinical Practice in Spain: Results from a Nationwide Series of 236 Patients

Introduction: Over half of patients with chronic myeloid leukemia (CML) in sustained deep molecular remission do not lose the major molecular response (MMR) after stopping treatment with tyrosine kinase inhibitors (TKI). This strategy is safe in controlled clinical trials, but there is scarce information on its applicability in the real-life setting. We aimed to assess if treatment cessation was feasible in clinical practice in a large nationwide series of CML patients from Spain.Methods: This retrospective study comprised a series of 236 patients in chronic-phase CML who discontinued TKI treatment outside of clinical trials between April 2009 and February 2018 in 33 Spanish institutions. Inclusion criteria were: a) TKI treatment duration >3 years; b) sustained MR4.5 in >4 consecutive determinations (one single point in MR4 was acceptable) during >2 years; c) molecular monitoring in a reference laboratory expressing the results on the International Scale (IS). Patients who had undergone allogeneic hematopoietic stem-cell transplantation were excluded. Molecular relapse was defined as consecutively detectable BCR-ABL1 transcripts showing a ≥1 log increase or loss of MMR in any single sample. Treatment-free remission (TFR) was estimated by the method of Kaplan-Meier and defined as the time from TKI discontinuation to the date of restarting therapy for any reason or, if treatment was not restarted, the date of last contact. Incidence of molecular relapse was calculated using the cumulative incidence function with resumption of TKI treatment in the absence of molecular relapse and death in MMR as competing events. Analysis of factors predicting molecular relapse was done by the method of Fine and Gray.Results: Table 1 shows the main characteristics of the series. Median follow-up from treatment discontinuation was 21.5 months, and 5 patients died in MMR due to CML unrelated causes. TKI therapy was reinitiated due to molecular relapse (MMR loss: n=52, increase >1 log in BCR-ABL transcript level at two consecutive assessments without losing MMR: n=12), patient preference (n=2), and severe withdrawal syndrome (n=1). One additional patient lost MMR after 20 months from treatment cessation but decided not to be retreated, with spontaneous recovery of MMR. The probability of TFR at 4 years was 64% (95% Confidence Interval [CI]: 55%-72%)(Figure 1). The cumulative incidence of molecular recurrence was 33% (95% CI: 26%-38%) at 3 years (Figure 2). Forty-nine relapses (75% of total) occurred in the first 6 months. The latest MMR loss was detected 30 months after treatment stop. One patient restarted treatment 44 months after TKI discontinuation due to ≥1 log increase in BCR-ABL1 transcripts in two consecutive samples without losing MMR. In univariate analysis, duration of TKI treatment of less than 5 years (P=0.005) and time in RM4.5 shorter than 4 years before TKI discontinuation (P=0.003) were both significantly associated with a higher incidence of molecular recurrence.No patient progressed to the advanced phases of CML. At the time of restarting treatment, the median BCR-ABL1 IS was 0.3%, with this value being >5% in only 7 instances. Most patients (81%) received the same TKI that they were taking before the trial of treatment cessation. Median follow-up after treatment resumption was 20 months. Among the 64 patients who restarted treatment due to molecular relapse, 46 of 52 cases regained MMR after a median time of 3 months, and 47 of 64 regained MR4.5 after a median time of 5 months. Response status at last control was: MR4.5 (n=196), MR4 (n=15), MMR (n=14), complete cytogenetic response (n=10), and other (n=1).Fifty-one patients (22%) developed musculoskeletal or joint pain after treatment cessation. In patients stopping imatinib, a significant increase in Hb levels, leukocyte counts, total lymphocyte counts, platelet counts, and cholesterol levels was observed. At 6 months, an increase in Hb level >2 g/dL was observed in 47% of patients with anemia. By contrast, nilotinib discontinuation was not followed by any relevant change in laboratory values.Conclusions: Our results confirm that treatment discontinuation is feasible and safe in clinical practice in Spain. Duration of TKI treatment of less than 5 years and a time in RM4.5 shorter than 4 years before TKI discontinuation were significantly associated with a higher incidence of molecular recurrence. DisclosuresHernandez Boluda:Incyte: Consultancy; Novartis: Consultancy. García Gutiérrez:Incyte: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding; BMS: Honoraria, Research Funding; Novartis: Honoraria, Research Funding. Ferrer Marin:Incyte: Consultancy; Novartis: Consultancy, Research Funding. Cervantes:Celgene: Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Hospital Clinic Barcelona: Employment.

P1-244 - Discontinuation of BCR-ABL tyrosine kinase inhibitors in patients with chronic myeloid leukemia: a retrospective study

BCR-ABL tyrosine kinase inhibitors (TKIs) have dramatically improved the treatment of chronic myeloid leukemia (CML). In several recent trials, TKIs were successfully discontinued in approximately half of patients who had achieved a deep molecular response. In clinical practice, patients occasionally discontinue TKIs. However, their outcomes are rarely reported. In this study, we analyzed the treatment-free remission (TFR) rate of such patients. We retrospectively evaluated data from patients with CML who were treated with TKIs between January 2001 and December 2016. The TFR rate was estimated using the Kaplan-Meier method. Eight out of 62 patients had discontinued TKI treatment. Their characteristics were as follows: male/female ratio, 5/3; median age, 71 (range, 40-81); median duration of treatment prior to discontinuation, 75 months. The reasons for discontinuation were progression of anemia (2), ischemic heart disease (1), pleural effusion (1), dementia (1), osteomyelitis (1), economic problems (1), and conception (1). Three of the 8 patients who discontinued TKI resumed treatment after a median of 3 months (range, 2-5) because of molecular relapse. The remaining 5 patients maintained MR4 (≥4 log reduction; BCR-ABL1 ≤0.01%) for a median of 16 months (range, 14-26). The TFR rate was 62% at 12 months. Those who maintained TFR tended to have a longer duration of treatment prior to cessation (median, 120 months; range, 37-159) than those who had molecular relapse (median, 36 months; range, 18-63; Mann-Whitney, p = 0.143), with an MR4.5 (≥4.5 log reduction; BCR-ABL1≤0.0032%) duration of 45 and 21 months (Mann-Whitney, p = 0.0714), respectively. All patients with molecular relapse experienced remission after resuming TKI. Patients who had a longer duration of treatment before TKI cessation maintained MR4.5 longer than those who relapsed. The TFR rate after cessation was comparable to results from previous clinical trials.

A Randomized Phase II Trial of Interferon (IFN)/GM-CSF Versus K562/GM-CSF Vaccination in Chronic Phase CML Patients on Frontline Tyrosine Kinase Inhibitor (TKI) Therapy: Potential of IFN to Enhance Molecular Remissions

Background: Tyrosine kinase inhibitors (TKIs) have dramatically improved outcomes in chronic myeloid leukemia (CML), but most patients either never achieve a complete molecular remission (CMR) or recur upon TKI discontinuation due to the persistence of leukemic stem cells. The kinetics of the initial TKI response appear predictive of long term outcomes as front-line imatinib patients who achieve a major molecular response (MMR) at 12 months have a 72% chance of attaining a CMR versus just 5% for those who do not (median time on Imatinib (IM) prior to CMR 66 months) (Branford. Clin Cancer Res. 2007). Interestingly, patients who achieve and maintain a CMR for ≥2 years on single agent IM have been the subject of several TKI discontinuation trials demonstrating that 38-47% of such patients maintain treatment-free remissions (TFR) at 2 years (median time on IM prior to discontinuation of 50-70 months) (Mahon. Lancet Oncol. 2010 and Ross. Blood. 2013). Interferon-alpha (IFN) and K562/GM-CSF vaccines have been shown to enhance the frequency of deep molecular responses to TKIs (Preudhomme. N Engl J Med. 2010 and Smith. Clin Cancer Res. 2010). We have shown that IFN targets LSCs, which may be the mechanism of improved IM responses (Angstreich. Br J Haematol. 2005). We now report initial outcomes for patients randomized between these treatments as a means of achieving TFR.Methods: Patients with Ph+ CML in complete cytogenetic remission on first-line TKI treatment for ≥1 year were randomized to receive either K562/GM-CSF vaccination at 3 week intervals (vaccine) or daily interferon/GM-CSF (IFN/GM) in combination with their TKI. If CMR was achieved after a minimum of 6 months of adjuvant treatment, then all therapy was stopped, and monthly BCR-ABL PCR testing was performed to monitor for relapse. Based on the limits of detection of our assay, CMR is defined as at least MR4.3, which is IS <0.01. At disease recurrence, or if CMR was not achieved at 12 months of combination therapy, patients were allowed to cross-over. The treatment arms were defined as IFN alone (A), vaccine alone (B), IFN followed by vaccine (C), or vaccine followed by IFN (D).Results: 34 patients were enrolled with final treatment allocation shown in Table 1. Most patients were on IM (n=31), nilotinib (n=2) and dasatinib (n=1) with a median duration of TKI use at enrollment of 19 (range 12-80) months. Both arms of the trial were well-tolerated. The vaccine arm was notable for grade 1 and 2 injection site reactions in all patients. Predictably, the IFN arm produced grade 1 and 2 myalgias and flu-like symptoms in the majority of patients. Three patients had to discontinue treatment on the IFN arm due to grade 3 adverse events including a neurological event of unknown causality (1) and ALT elevation (2). Table 1 shows the responses by treatment arm with 62% of patients achieving CMR at a median of 28.6 (range 11-100) months of TKI therapy (compared to 66 months in IRIS). 15 patients (44%) discontinued TKI treatment per study plan after a median of 27.5 (range 19-56) months of TKI treatment (compared to median of 50-70 months of TKI in STIM/TWISTER), and 4 patients (27%) remain off therapy with TFRs of 64, 64, 85, and 92 months. Those with recurrence were off TKI for a median of 3 (range 1-5) months. Importantly, the long term responders who achieved CMR with adjuvant therapy all received IFN adjuvant, and all had relatively little prior TKI treatment (21, 27, 28, and 44 months) compared to published discontinuation studies. As expected in this group, all 4 had achieved a MMR at 12 months on TKI alone (p=0.05). What was unexpected was that 50% of patients treated with one of the IFN arms who had not achieved a MMR at 12 months on TKI alone went on to CMR after treatment on study compared to previous reports and just 15% of historical controls in our institutional database who achieved CMR on TKI alone (p=0.02)Conclusions: Adjuvant therapies may improve the likelihood of achieving CMR and allow for discontinuation of TKI in CML patients with minimal TKI exposure. Even patients predicted to not achieve CMR based on a lack of MMR at 12 months did so at a higher rate than expected following IFN treatment. IFN likely played a role in long term TFR in 4 exceptional responders who successfully discontinued IM sooner than in previously reported discontinuation trials, possibly owing to IFNs effect on primitive CML progenitors. [Display omitted] DisclosuresSmith:Actinium Pharmaceuticals, Inc.: Research Funding.

Peripheral Blood Flow-Cytometry Chronic Myeloid Leukemia Stem Cells Detection and Quantification during Tyrosine Kinase Inhibitors Therapy

Introduction: In chronic myeloid leukemia (CML), tyrosine Kinase Inhibitors (TKIs) treatment is a potentially life-time therapy for the majority of patients (pts), as few of them, only after achieving a deep and stable molecular response, may discontinue TKIs without recurrence of disease. Available data suggest that relapse after TKIs discontinuation is due to the persistence of leukemic stem cells (LSCs) intrinsically resistant to TKIs. Survival of CML LSCs may be the consequence of activation of several pathways BCR-ABL1 independent. qRT-PCR, the most sensitive assay to monitor disease status in CML pts, may be inappropriate to quantify residual quiescent CML LSCs that are transcriptionally silent. Therefore, the possibility to easily quantify LSCs during TKIs treatment is a great opportunity to better understand the behavior of residual LSCs and potentially to identify those pts candidates to safely discontinue TKIs. Recently, Valent et al described that CD34+/CD38-/Lin- CML LSCs specifically co-express dipeptidylpeptidase IV (CD26) and that CD26 is a potential biomarker for the quantification and isolation of CML LSCs, in bone marrow samples of CML patients. Furthermore, Culen et al. quantified CD26+ LSCs bone marrow compartment in 31 CML patients at diagnosis and their number appears to correlate with response to TKIs treatment. In the present study we wanted to explore the feasibility, rate and potential implication of detecting CD26+ LSCs in peripheral blood (PB) from CML pts during TKI treatment.Methods: CML pts during first line treatment with any approved TKIs, referring to several Italian Hematology Centers, entered this non interventional cross sectional study after signing a proper informed consent. During a routine follow up visit, in which pts were checked for molecular response by standard PB qRT-PCR BCR-ABL1 analysis, additional 3 mls of PB were collected in EDTA and sent within 24 hours to Siena Hematology Lab to detect CD34+/CD38-/CD26+ LSCs by multicolor flow cytometry. After red blood cells lysis, cells were incubated with anti CD45 (BD Biosciences), CD34 (581), CD38 (HIT2), CD26 (M-A261) (BD Pharmigen). After washing, acquisition and analysis were performed by FACSCanto II (BD Biosciences, NR Nannini) using DIVA 8 software (BD, Biosciences). CD45+ cells acquired for each sample ranged from 500,000 to 1,000,000. Isotype controls were included in each staining. In 5 pts a FISH analysis of PB sorted CML LSCs population was also performed.Results: to validate our assay we first performed a FISH analysis of both PB sorted CD34+/CD38-/CD26+ and CD34+/CD38-/CD26- in 5 CML patients at 3-6 months after starting treatment, confirming Ph+ cells only in the CD26+ fraction. Afterward, we checked for circulating CML LSCs a total of 202 CML pts in first line treatment with TKIs for a median of 39 months (range 1-175). Type of TKI, length of treatment, molecular response and quantification of LSCs are summarized in Table 1. PB CML LSCs were detectable in 146/202 (72.3%) pts with a median number of CD26+ of 0,0165 cells/µL (range 0,0018-0,66). Kendall rank correlation coefficient used to analyze the relation between the measurable variables showed no correlation between BCR-ABL/ABLIS ratio (median 0,004 range 0-61) and number of residual LSCs (r 0.118 p=0.097). In 56/202 (27.7%) pts CD26+ LSCs were undetectable, yet we found no correlation with the concomitant degree of molecular response.Conclusions: this study represents the first attempt to measure in a large cohort of CML patients residual circulating LSCs during TKIs treatment. In our hands PB LSCs flow-cytometry assay appeared feasible, specific and sensitive and thus suitable for routine monitoring. As expected, the majority of CML patients, even in deep molecular response, still harbor residual LSCs and the number of PB CD26+ did not correlate with the number of BCR-ABL1 copies. This evidence suggests that the molecular response refers to transcriptionally active CML progenitor cells and not to quiescent, TKIs resistant, CML LSCs. Prospective studies evaluating the behavior of PB CML LSCs during different TKIs treatment, as well as studies monitoring PB CD26+ in CML pts that discontinued TKIs treatment are ongoing. Our goal is to rule out the impact, if any, of a "stem cell response" in addition to the standard molecular response in the management of CML patients mainly to identify those pts candidates for a safe TKI discontinuation. [Display omitted] DisclosuresBocchia:Janssen: Honoraria; Novartis: Honoraria; Bristol-Myers Squibb: Honoraria. Aprile:Novartis: Honoraria. Castagnetti:Pfizer: Consultancy, Honoraria; Bristol-Myers Squibb: Consultancy, Honoraria; ARIAD Pharmaceuticals: Consultancy, Honoraria; Novartis: Consultancy, Honoraria. Tiribelli:Ariad Pharmaceuticals: Consultancy, Speakers Bureau; Novartis: Consultancy, Speakers Bureau; Bristol-Myers Squibb: Consultancy, Speakers Bureau. Breccia:Novartis: Consultancy, Honoraria; Bristol Myers Squibb: Honoraria; Celgene: Honoraria; Ariad: Honoraria; Pfizer: Honoraria. Rosti:Roche: Honoraria, Research Funding, Speakers Bureau; Incyte: Honoraria, Research Funding, Speakers Bureau; Pfizer: Honoraria, Research Funding, Speakers Bureau; BMS: Honoraria, Research Funding, Speakers Bureau; Novartis: Honoraria, Research Funding, Speakers Bureau.

Mature, Adaptive-like CD56DIM NK Cells in Chronic Myeloid Leukemia Patients in Treatment Free Remission

▪Background: Tyrosine kinase inhibitors (TKIs) have significantly improved the treatment of CML. Even though TKI treatment is generally not considered curative, recent studies have shown that nearly half of CML patients who have achieve good and durable responses are able to stop the TKI treatment. However, patients who have successfully discontinued TKI treatment still have residual disease. We hypothesized that the immune system plays a role in treatment free remission (TFR), and our preliminary results in the EURO-SKI trial showed that patients who relapse early after imatinib discontinuation have decreased numbers and frequencies of NK cells. In EURO-SKI trial relapse was defined as the loss of major molecular response (MMR). We now aimed to analyze in more detail the phenotype and function of the NK cells in order to understand their role in TFR.Methods: Lymphocyte subclass analysis (the number of NK-, T- and B-cells) was performed at the time of therapy discontinuation and 1 month after the imatinib discontinuation in patients participating in the EURO-SKI stopping trial in the Nordic countries (n=105, results are presented from patients who have reached 6 months follow-up). More detailed immune phenotype and functional assays (NK-cell degranulation and secretion of Th1 type of cytokines IFN-γ/TNF-α) were analyzed from a proportion of patients (n=31).Results: Imatinib treated patients remaining in remission for 6 months (non-relapsing, n=48, median age 60,5 years) displayed an increased amount of NK cells at the time of drug discontinuation (18.6% vs. 11.0%, p=0.02, NK-cell count 0.25 x109 cells/L vs. 0.184 x109 cells/L m, p=0.059) compared to patients who relapsed early (before 5 months, n=29, median age 60,5 years). Furthermore, the NK cell frequency in non-relapsing patients was even higher than in healthy controls (11.5%, n=48, p=0.001). T and B cell counts and frequencies showed no differences between the groups.Detailed analysis of the NK cell compartment displayed a more mature phenotype for the NK cells in non-relapsing patients. Larger frequencies of NK cells from early relapsing patients was CD56bright compared to non-relapsing patients (4.8% vs. 2.7% of CD56 NK cells, p=0.04). Furthermore, patients who had higher frequencies of CD56bright NK cells than median had decreased TFR at 6 months (42%) compared to patients with lower frequency (70%, p=0.01). In addition, there was a trend towards more CD57pos (78% (n=21) vs. 66% (n=10), p=0.09) CD56dim NK cells in non-relapsing patients.To further study the mature NK cells in non-relapsing patients, recently identified markers (FceRgneg, PLZFneg, SYKneg, EAT-2neg) for adaptive NK cells were analyzed. Interestingly, there was a trend that non-relapsing patients had higher frequencies of adaptive-like NK cells. For example, non-relapsing patients had more CD56dim NK cells that had down regulated EAT-2 (2.8% (n=6) vs. 1.3% (n=5) of lymphocytes, p=0.03) and more CD56dim NK cells expressing NKG2D (11.2% vs. 2.6% of lymphocytes, p=0.02) and NKp46 (13.6% vs. 3.9% of lymphocytes, p=0.05). Moreover, after imatinib discontinuation the expression of transcription factor Eomes increased in the CD56dim NK cells of the early relapsing group (baseline MFI 2045 vs. 1 month 3480, p=0.06), while in non-relapsing group it seemed to even decrease (baseline MFI 2273 vs. 1 month 1980, p=0.13) pointing towards an adaptive phenotype.No significant differences between the groups were observed when degranulation against K562 cell line was studied. However, CD16neg NK cells from non-relapsing patients responded to K562 stimulation by secreting more TNFα/IFNγ compared to the early relapsing patients (21% vs. 13% of CD56pos CD16neg NK cells, p=0.01). Furthermore, patients whose CD16neg NK cells had higher than median TNFα/IFNγ secretion when stimulated with K562 cells showed an increased TFR at 6 months (78%) compared to patients who had lower TNFα/IFNγ secretion than median (37%, p=0.005).Conclusions: CML patients who successfully discontinued imatinib therapy displayed a higher number and frequency of peripheral blood mature, adaptive-like NK cells capable of secreting cytokines TNFα/IFNγ relative to relapsing patients. How such NK cells may contribute to maintenance of treatment free remission is still unknown. Nonetheless, our results warrant further clinical studies with NK-cell modulating agents. DisclosuresMuller:Novartis: Honoraria, Other: Consulting or Advisory Role, Research Funding; ARIAD Pharmaceuticals Inc.: Honoraria, Other: Consulting & Advisory Role, Research Funding; BMS: Honoraria, Other: Consulting or Advisory Role, Research Funding. Hjorth-Hansen:Novartis: Honoraria; Ariad: Honoraria; Bristol-Myers Squibb: Research Funding; Pfizer: Honoraria, Research Funding. Saussele:Pfizer: Honoraria, Other: Travel grant; BMS: Honoraria, Other: Travel grant, Research Funding; Novartis Pharma: Honoraria, Other: Travel grant, Research Funding; ARIAD: Honoraria. Mahon:ARIAD: Consultancy; Novartis: Consultancy, Honoraria; Bristol-Myers Squibb: Consultancy, Honoraria; Pfizer: Consultancy. Porkka:Bristol-Myers Squibb: Honoraria; Celgene: Honoraria; Novartis: Honoraria; Pfizer: Honoraria. Richter:Ariad: Honoraria; Bristol-Myers Squibb: Honoraria; Novartis: Honoraria. Mustjoki:the Finnish Cancer Societies: Research Funding; Pfizer: Honoraria, Research Funding; Academy of Finland: Research Funding; Sigrid Juselius Foundation: Research Funding; Finnish Cancer Institute: Research Funding; Signe and Ane Gyllenberg Foundation: Research Funding; Bristol-Myers Squibb: Honoraria, Research Funding; Novartis: Honoraria, Research Funding.

Unplanned discontinuation of tyrosine kinase inhibitors in chronic myeloid leukemia.

This study was conducted to investigate the outcomes of patients with chronic myeloid leukemia (CML) who discontinued tyrosine kinase inhibitor (TKI) treatment. A single-center retrospective analysis was performed, including 46 chronic-phase (CP) CML patients who achieved complete molecular response (CMR) with TKIs. TKI treatment was discontinued in 13 patients based on their requests. The BCR-ABL transcript levels were monitored in the peripheral blood by quantitative polymerase chain reaction analysis following treatment discontinuation. Of the 13 patients who discontinued TKI treatment, 7 remained in CMR, with a median follow-up of 26 months (range, 10-60 months). The remaining 6 patients lost CMR following TKI discontinuation; 2 of these patients achieved a second CMR following re-administration of TKIs, 2 patients spontaneously achieved CMR and 2 remained in complete hematological response (CHR) without TKI treatment with a median follow-up of 29.5 months (range, 10-52 months). In conclusion, the survival of patients who lost CMR following TKI discontinuation may not be affected, even without re-administration of TKIs. Vigilant observation is recommended for such patients. The limitations of this study included the small patient sample, retrospective design and patient heterogeneity. Therefore, the results must be interpreted with caution.

Disease Relapse After TKI Discontinuation In CML Is Related Both To Low Number and Impaired Function Of NK-Cells:Data From Euro-SKI

BackgroundThe inhibition of oncogenic BCR-ABL1 kinase with tyrosine kinase inhibitors (TKIs) has significantly improved the prognosis of CML. Recent reports suggest that approximately 40 % of CML patients who have achieved optimal therapy response (complete molecular remission, CMR) can stop imatinib treatment without recurrence of detectable BCR-ABL1 transcripts. However, no predictive prognostic factors for successful therapy discontinuation have yet been identified. We therefore set up an immunological substudy in the ongoing pan-European EURO-SKI stopping study. We aimed to identify predictive biomarkers for relapse and non-relapse after TKI discontinuation. In addition, we aimed to understand more on the mechanisms of immune surveillance in CML and to study the effects of TKI treatment on the immune system. Materials and methodsPatients in deep molecular remission (MR4, BCR-ABL < 0,01% IS) for at least one year and with TKI treatment for at least 3 years were eligible for the clinical study. Basic lymphocyte immunophenotyping (the proportions and absolute numbers of NK-, T- and B-cells) was performed at the university hospital laboratories at the time of therapy discontinuation, and 1, 6, and 12 months after the TKI discontinuation. In a proportion of patients a more detailed immunophenotypic (analysis of CD45RA, CD57, CD27 and CD62L expressions) and functional analyses were done from fresh blood samples in a central immunology laboratory (Helsinki) at the same time points. The cytotoxicity of NK-cells was studied by measuring the direct killing of target cells (K562) and by the degranulation assay (CD107a/b expression). The secretion of Th1 type of cytokines IFN-γ/TNF-α was studied from both T- and NK-cells. ResultsThus far the basic lymphocyte subclass measurement has been analyzed from 62 patients who have discontinued TKI treatment within the EURO-SKI study. Functional analyses have been performed from 30 patients. 60 patients have used imatinib before treatment discontinuation and 2 patients dasatinib.At baseline, before the treatment discontinuation both CD4+ and CD8+ T-cell counts were within the normal range (median CD4+ 0.73x 109/L, range 0.11-2.4x 109/L; CD8+ 0.35x 109/L, 0.07-1.92 x 109/L). The TKI stop had no significant numerical or functional effect on T-cells, and at 1 month time-point the median T-cell counts were unchanged (CD4+ 0.73x 109/L; CD8+ 0.35x 109/L). Similarly, at the baseline, the median NK-cell count was within a normal range (0.26 x 109/L, range 0.04-1.04 x 109/L), and no significant change was observed 1 month after stopping the treatment (median 0.29 x 109/L). Furthermore, at the baseline and at the 1-month time-point the cytotoxicity of NK-cells and the cytokine secretion of T- and NK-cells did not significantly differ from the healthy controls when all patients were considered as a one group.However, when patients were divided in two groups based on the relapse status, the patients who eventually relapsed had significantly fewer NK-cells already at the baseline (Figure A; absolute count 0.18x 109/L vs. 0.32 109/L, p=0.008; proportions 11% vs. 21%, p=0.001). The phenotype of NK-cells also differed between the two groups, and the patients who relapsed had less NK-cells expressing CD57 (median 58% vs. 69%, p=0.046) and CD16 (median 67% vs. 83%, p=0.018) on the cell surface. Furthermore, the cytotoxicity of NK-cells was impaired in patients who failed to discontinue the TKI treatment successfully and no killing activity was observed in their samples (Figure B; alive K652 cells after co-incubation with effector cells 100% vs. 88%, p=0.07). No clear differences were observed in the function or the numbers of T-cells between relapsing and non-relapsing patients. [Display omitted] ConclusionsThe NK-cell numbers and their function may predict disease relapse after TKI discontinuation. This may have impact on the future stopping trials. In addition, it further illustrates the importance of the immune system in the successful long-term treatment of CML. Disclosures:Ekblom:Novartis: Honoraria; Bristol-Myers Squibb: Honoraria. Hjorth-Hansen:Pfizer, BMS: Honoraria, Travel expenses Other. Porkka:BMS: Honoraria, Research Funding; Novartis: Honoraria, Research Funding. Richter:Bristol-Myers Squibb: Consultancy, Speakers Bureau; Novartis: Consultancy, Research Funding, Speakers Bureau. Mustjoki:Novartis: Honoraria; BMS: Honoraria, Research Funding.