Tyrosine Kinase Inhibitors Treatment Discontinuation Research Articles

Identification of Individual Risk Factors for Treatment Free Remission (TFR) Failure in Chronic Phase Chronic Myeloid Leukemia (CP-CML) Patients: Predictive Models Developed on a Nationwide Clinical and Claim Database

Introduction Over the past decade, the landscape of CML has been radically improved by the introduction of Tyrosine Kinase Inhibitors (TKI). However, since prolonged TKI treatment would reduce compliance, with associated risk of relapse and progression, and increased toxicities, patients (pts) who achieve and maintain a deep molecular response can now attempt TKI treatment discontinuation to achieve TFR. As TFR attempts may fail due to loss of major molecular response and imply restart of TKI therapy, it is essential to study individual factors associated with TFR outcome and to develop predictive models to provide TFR outcome likelihood with respect to pts' characteristics. Methods Predictive models of TFR failure at 6, 12, 24 and 36 months after TFR attempts were developed on 2 populations: (i) on CP- CML pts managed in a reference center for CML who attempted TFR between January 2003 and January 2023, named CML-pts and (ii) on those CML-pts for which an individual indirect linkage to nationwide claim database succeeded, named CML-linked-pts. The model was thus developed based (i) on clinical data exclusively (demographics, CML characteristics, TKI lines, molecular response), and (ii) on clinical data combined with claim data, which provided information on comorbidities, other treatments than TKI and any healthcare resource use (HCRU) of interest. Correlation and features' predictive power was assessed through Pearson's correlation and predictive power scores (PPS). Logistic regression model and machine learning algorithms (k-nearest neighbor, support vector machine, single decision tree, random forest, multilayer perceptron, and gradient boosting machine) were used. Nested k-fold cross-validation (CV) was used to assess the robustness of the algorithms over all data and hyperparameter optimization was performed. Features' contribution to predict TFR outcomes were assessed using SHAP (“SHapley Additive exPlanations”) values. Results Analysis on (i) 208 CML-pts, who attempted 250 TFR - 208 first attempts (TFR 1), 42 second attempts (TFR 2). Median age was 59.6 (IQR:20.6) and 60.6 (IQR:18.2) years at TFR 1 and TFR 2, respectively, and M/F sex ratio was 1.17 and 1.1. The overall proportion of TFR failure was 35.6%, 43.6%, 46.8% and 48.8% at 6, 12, 24, and 36 months, respectively. Analysis on (ii) 118 CML-linked-ptss, who attempted 134 TFRs (110 TFR 1 24 TFR 2). Median age was 61.5 (IQR: 21.1) and 61.4 (IQR: 12.0) years at TFR 1 and TFR 2, respectively, and M/F sex ratio was 1.04 and 1.18. The proportion of TFR failure was 35.0%, 43.2%, 46.2% and 49.3% at 6, 12, 24 and 36 months, respectively. Studied predictive variables, in both populations (i) and (ii), had little correlation with TFR outcomes, ranging respectively from (i) -0.2 to 0.2 and (ii) -0.16 to +0.31, with poor predictive power (PPS from (i) 0 to 0.19, (ii) 0 to 0.25). Overall, predictive models hardly correctly predicted TFR failure - with sensitivity below 50% and were stronger at rather predicting absence of TFR failure - with specificity above 80%. Best performances were obtained with logistic regression model for both populations, for predicting at 6 and 12 months for population (i) and 6 months for population (ii). Accuracies were 72% for population (i) - with F1-score (i.e., model's ability to predict failure) of 50.0% at 6 months and 69.6% at 24 months -, and 77.8% for population (ii) - with F1-score 66.7% at 6 months. SHAP values showed that attempting a second TFR was the most predictive factor of TFR failure for both populations (i) and (ii) (see Figure 1). Sensitivity analyses considering only TFR 1 in the models showed no improvement in performance. Conclusion Although this study was conducted on one of the largest TFR cohorts ever studied, prediction abilities of the models for TFR failure at the different time points were not sufficient to be proposed as a decision support tool, when developed with either clinical data or with both clinical and claim data. The models were indeed able to predict success but did not manage to find patterns to predict failure; only TFR number had predictive power of TFR outcome. Besides, claim data did not provide HCRU-related predictive factors. Among study limits, this monocentric cohort would reflect homogeneous practices in a same center. Analysis on larger cohorts of patients from different centers would potentially allow the capture of more variability in clinical practices.

A Real-World Evidence-Based Study of Long-Term Tyrosine Kinase Inhibitors Dose Reduction or Discontinuation in Patients with Chronic Myeloid Leukaemia.

The therapeutic approach to chronic myeloid leukaemia (CML) has changed in recent years. As a result, a high percentage of current patients in the chronic phase of the disease almost have an average life expectancy. Treatment also aims to achieve a stable deep molecular response (DMR) that might allow dose reduction or even treatment discontinuation. These strategies are often used in authentic practices to reduce adverse events, yet their impact on treatment-free remission (TFR) is a controversial debate. In some studies, it has been observed that as many as half of patients can achieve TFR after the discontinuation of TKI treatment. If TFR was more widespread and globally achievable, the perspective on toxicity could be changed. We retrospectively analysed 80 CML patients treated with tyrosine kinase inhibitor (TKI) at a tertiary hospital between 2002 and 2022. From them, 71 patients were treated with low doses of TKI, and 25 were eventually discontinued, 9 of them being discontinued without a previous dose reduction. Regarding patients treated with low doses, only 11 of them had molecular recurrence (15.4%), and the average molecular recurrence free survival (MRFS) was 24.6 months. The MRFS outcome was not affected by any of the variables examined, including gender, Sokal risk scores, prior treatment with interferon or hydroxycarbamide, age at the time of CML diagnosis, the initiation of low-dose therapy and the mean duration of TKI therapy. After TKI discontinuation, all but four patients maintained MMR, with a median follow-up of 29.2 months. In our study, TFR was estimated at 38.9 months (95% CI 4.1-73.9). This study indicates that low-dose treatment and/or TKI discontinuation is a salient, safe alternative to be considered for patients who may suffer adverse events (AEs), which hinder the adherence of TKI and/or deteriorate their life quality. Together with the published literature, it shows that it appears safe to administer reduced doses to patients with CML in the chronic phase. The discontinuation of TKI therapy once a DMR has been reached is one of the goals for these patients. The patient should be assessed globally, and the most appropriate strategy for management should be considered. Future studies are needed to ensure that this approach is included in clinical practice because of the benefits for certain patients and the increased efficiency for the healthcare system.

Chronic myeloid leukemia: where do we stand, where can we go?

The introduction of BCR-ABL tyrosine kinase inhibitors to the treatment of chronic myeloid leukemia (CML) has significantly changed the long term therapy results. After an initial 12 months of therapy with tyrosine kinase inhibitor (TKI), a 3-log reduction of the BCR-ABL copies number on an international scale is possible in 22–46% of patients, depending on the TKI used. In TKI-responsive patients, long-term TKI treatment results are even better, with the BCR-ABL transcript level decreasing over time, even to the point of becoming undetectable. Therefore, an operational cure can be diagnosed in CML patients with an optimal response to 1 st -line TKI treatment, atherapy duration of longer than 5–8 years, and BCR-ABL transcript level below MR4.0–MR4.5 for a period of more than two years. The latter has been the basis of multiple concepts of permanent or periodic discontinuation of TKI treatment [treatment-free remission (TFR)]. Initial TKI discontinuation clinical trials resulted in satisfactory results, with a disease recurrence rate of c.40–60% after 2–3 years. The mechanism of disease recurrence was then studied , with detailed characterization of the CML stem cells (CML SCs) immunophenotype and the mechanisms of survival and self-renewal under TKI selective pressure. A better understanding of the biology of CML allowed the formulation of new therapy concepts of CML SCs eradication, and new criteria for successful TFR qualification.

Deep molecular response on imatinib treatment — results from a real-life retrospective study

Introduction: Tyrosine kinase inhibitors (TKIs) have dramatically changed the outcome of chronic myeloid leukemia (CML) patients. Recent research focused on TKI discontinuation after achieving a deep molecular response (DMR) has revealed that about half of the patients maintain the response. DMR is a key criterion for TKI discontinuation. Our retrospective, ‘real-life’ study was aimed at to estimating the proportion of patients treated with first-line imatinib (IM) who achieved DMR and thus may be candidates for discontinuation of TKI treatment in a real life setting. Material and methods: Two hundred and twenty-three patients were enrolled. All patients started IM at 400 mg daily. The median age at the time of diagnosis was 57 years (range: 17–92). Results: Eighty-five patients (43%) in the whole group achieved DMR. Early molecular response (EMR) was achieved by 136 (69%) patients and correlated with the DMR rate (53% with EMR vs 14% without, p < 0.001). Major molecular response (MMR) after a year of treatment was confirmed in 108 (55%) patients, and was predictive for achieving DMR at any time (69% with MMR vs. 24% without, p < 0.001). Conclusion: DMR can be achieved in a significant proportion of patients in a real-life setting. We observed that both the achievement of an EMR at three months and MMR at 12 months were associated with a significant advantage in terms of DMR.

Continued Discontinuation of TKI Treatment in Medullary Thyroid Carcinoma - Lessons From Individual Cases With Long-Term Follow-Up.

BackgroundThe tyrosine kinase inhibitors (TKI) vandetanib and cabozantinib are approved as targeted therapies in advanced medullary thyroid carcinoma (MTC) with symptoms or high tumour burden. Only recently, toxicity in long-time TKI usage was analysed. However, little is known about the impact of TKI discontinuation on MTC disease course after longer-term therapy. Here, we report our experience in a series of 7 MTC patients with vandetanib treatment of up to 87 months followed by discontinuation for concerns of toxicity or due to side-effects. The discontinuation of TKI therapy is a relevant clinical scenario. To our knowledge we present the largest single center series on an important aspect of TKI management.MethodsRetrospective analysis of MTC patients with continued discontinuation of vandetanib treatment in a tertiary referral endocrine tumour centre. Analysis included a review of patients’ records for TKI indication, and treatment response as well indications for continued TKI discontinuation and follow-up by clinical assessment, calcitonin and CEA doubling times as well as imaging (ultrasound, CT).ResultsSeven MTC patients [6 sporadic MTC, 1 Multiple Endocrine Neplasie Type 2a (MEN2a)] with previous vandetanib treatment (median: 41 months; range 7-87 months) and continued TKI discontinuation were identified out of 161 analysed MTC files. TKI treatment was initiated due to high tumour burden and symptoms or RECIST (Response Evaluation Criteria In Solid Tumors) progression in all patients. Two patients (29%) remained stable after discontinuation of vandetanib until now (follow-up of 47 and 61 months). Both patients had been on TKI therapy for 73 and 58 months. Five patients (71%) developed progressive disease after TKI discontinuation. In 2 patients, vandetanib was restarted after 45 and 52 months resulting again in disease control. One patient was enrolled in a new RET kinase inhibitor trial after 45 months of vandetanib discontinuation. Two patients declined restart of treatment due to mental health issues leading to discontinuation of vandetanib in the first place (after 7 and 38 months of treatment) and both patients died of rapidly progressive disease. At time points of tumour progression, calcitonin-doubling time (CDT) was < 2 years in all patients.ConclusionThis case series suggests that discontinuation of long-term vandetanib treatment with documented stable disease does not automatically result in rapid disease progression but may be followed by prolonged “TKI free” stable disease in individual patients. Analysis of calcitonin and CDT during discontinuation is indicated as it will unmask tumour progression earlier than imaging. Restart with the same TKI is possible in case of progression.

Digital droplet PCR as a predictive tool for successful discontinuation outcome in chronic myeloid leukemia: Is it time to introduce it in the clinical practice?

Tyrosine kinase inhibitors (TKIs) have drastically changed the outcome of chronic myeloid leukemia (CML) patients. A sustained and deep molecular response achieved over time paves the way to therapy discontinuation, and is a pre-requisite to attempt treatment-free remission. Monitoring of the molecular response during treatment discontinuation is routinely carried out by RQ-PCR, but it may not be the optimal tool to monitor minimal residual disease at the time of stopping treatment and during treatment discontinuation. Different digital PCR platforms (such as droplet dPCR) are available, a method based on water-emulsion droplet technology in which the sample is partitioned into 20,000 droplets and PCR amplification of the template subsequently occurs in each individual droplet. The consequent high sensitivity and precision with a very reliable quantification without the need of a calibration curve and the exquisite reproducibility makes this procedure as an ideal alternative method for the detection of very low levels of disease. Aim of this review is to describe and discuss the recent use of dPCR/ddPCR in CML, focusing in particular on its role in TKI treatment discontinuation strategies.

Predictive indicators of successful tyrosine kinase inhibitor discontinuation in patients with chronic myeloid leukemia.

Clinical trials have demonstrated that some patients with chronic myeloid leukemia (CML) treated for several years with tyrosine kinase inhibitors (TKIs) who have maintained a molecular response can successfully discontinue treatment without relapsing. Treatment free remission (TFR) can be reached by approximately 50% of patients who discontinue. Despite having similar levels of deep molecular response and an identical duration of treatment, the factors that influence the successful discontinuation of CML patients remain to be determined. In this review we will explore the factors identified to date that can help predict whether a patient will successfully achieve TFR. We will also discuss the need for the identification of predictive biomarkers associated with a high probability of achieving TFR for the future personalized identification of patients who are suitable for the discontinuation of TKI treatment.

FDA- and EMA-Approved Tyrosine Kinase Inhibitors in Advanced EGFR-Mutated Non-Small Cell Lung Cancer: Safety, Tolerability, Plasma Concentration Monitoring, and Management.

Non-small-cell lung cancer (NSCLC) is the most common form of primary lung cancer. The discovery of several oncogenic driver mutations in patients with NSCLC has allowed the development of personalized treatments based on these specific molecular alterations, in particular in the tyrosine kinase (TK) domain of the epidermal growth factor receptor (EGFR) gene. Gefitinib, erlotinib, afatinib, and osimertinib are TK inhibitors (TKIs) that specifically target EGFR and are currently approved by the Food and Drug Administration (FDA) and the European Medicines Agency (EMA) as first line treatment for sensitive EGFR-mutant patients. However, these four drugs are associated with severe adverse events (AEs) that can significantly impact patient health-related quality of life and patient monitoring. EGFR-TKIs are commonly used together with other types of medication that can substantially interact. Here, we review approaches used for the management of TKI-AEs in patients with advanced NSCLC to promote the benefits of treatments and minimize the risk of TKI treatment discontinuation. We also consider potential TKI–drug interactions and discuss the usefulness of plasma concentration monitoring TKIs based on chromatographic and mass spectrometry approaches to guide clinical decision-making. Adjusting the most appropriate therapeutic strategies and drug doses may improve the performance therapy and prognosis of patients with advanced EGFR-mutated NSCLC.

PB1934 QUALITY OF LIFE IN CHRONIC MYELOID LEUKEMIA PATIENTS WITH DEEP MOLECULAR RESPONSE AFTER STOPPING TREATMENT BY TYROSINE KINASE INHIBITORS AT LONG‐TERM FOLLOW‐UP

Background:It is reasonable to incorporate the quality of life (QoL) assessment into the comprehensive evaluation of treatment outcomes in chronic phase chronic myeloid leukemia (CML CP) patients (pts) with deep molecular response (DMR) who enter the treatment‐free remission (TFR) phase and stop therapy by tyrosine kinase inhibitors (TKIs).Aims:We aimed to study QoL in CML CP pts who had stable DMR at long‐term follow‐up.Methods:The CML CP pts who had received therapy by any TKI ≥ 3 years (yrs) and had maintained DMR (MR4 or deeper with BCR‐ABL ≤0.01% IS) were enrolled into the prospective multicenter study RU‐SKI which has been conducted within the clinical approbation supported by Ministry of Health of RF. TKI were resumed in a case of major molecular response (MMR, BCR‐ABL&gt;0.1% IS) loss. The QoL questionnaires RAND SF‐36 and EORTC QLQ C30 were filled out by the pts before stopping TKI treatment (base‐line) and at different time points after TKI treatment discontinuation. QoL analysis was performed in patients who were in TFR lasting &gt;12 months. The paired Wilcoxon test was used for the statistical analysis.Results:In total, 98 CML CP pts with DMR were enrolled in the trial. Mean age was 46 yrs; 48% were males; 13% had high Sokal risk score; 80.6% pts were with comorbidity. The TKIs before treatment cessation were the following: imatinib in 67 (78%) pts, second‐generation (2G) TKIs were used as 1st line and as 2nd line in 11 (11.2%) and in 20 (20,4%) pts respectively. Toxicity to TKI was revealed in 62/98 pts (63.2%). During TFR phase TKI withdrawal syndrome was observed in 41/98 pts (41.8%). Me TFR duration was 24 mos (range 14–42). MMR loss and TKI resuming was in 46 (47%) pts. In QoL analysis at long term follow‐up 51/98 pts were included. In the vast majority of pts (46/51) during TFR phase QoL scores improved (11.8%) or were stable (78.4%) as compared with base‐line. Physical functioning (80.7 vs 87.2) and general health (63.3 vs 69.7) significantly improved (p≤0.01); Integral QoL Index (IQoLI) increased from 0.575 to 0.633 (p &lt; 0.05). Also significant decrease of fatigue, nausea/vomiting, shortness of breath and sleep disturbance during long‐term TFR was revealed (p &lt; 0.05). To note, five pts who exhibited QoL worsening at long‐term follow‐up after stopping treatment (57% decrease of mean IQoLI as compared with base‐line) had toxicity to TKI, TKI withdrawal syndrome and comorbidities.Summary/Conclusion:In general, the positive QoL changes and decrease of symptom burden was revealed in the majority of CML CP pts who maintained stable MMR and were off‐treatment for more than 12 months. Toxicity to TKI, TKI withdrawal syndrome and comorbidities may be accompanied with unfavorable QoL changes in CML CP pts at long‐term follow‐up after TKI stop therapy. The results of QoL assessment may contribute to optimization of the treatment strategies of CML patients with DMR.

Role of Folate Receptor 3 in Tyrosine Kinase Inhibitor Discontinuation in Chronic Myeloid Leukemia

Chronic myeloid leukemia (CML) is a clonal myeloproliferative disorder characterized by Philadelphia chromosome and its molecular counterpart, the BCR-ABL1 fusion gene. Discontinuation of tyrosine kinase inhibitors (TKIs) therapy after achieving a persistent deep molecular response (DMR) is an urgently-needed treatment goal for patients and it was written in NCCN guideline Version 2.2017 for CML. Indeed, various studies have confirmed the feasibility of stopping TKIs therapy in many regions. However, increasing evidence demonstrated that TKIs are unable to eliminate quiescent leukemic stem cells (LSCs), which lead to treatment resistance or relapse after discontinuation of TKIs treatment. Multiple works have confirmed that approximately 50-60% of DMR patients stopping TKIs will lose their response and require retreatment. The patients who will lose the treatment-free remission (TFR) remains unknown currently.We selected bone marrow of 14 patients (matched 7 relapse and 7 non-relapse patients) who discontinued TKIs therapy in our center for transcriptome analysis to discover the differences between relapse and non-relapse patients. Bioinformatics indicated that folate receptor 3 (FOLR3) was highly expressed in non-relapse patients and only in the non-relapsers (Figure 1A). Further work found these samples all carried a common SNP mutation. Then we respectively transferred newly diagnosed chronic phase (CP) CML patients derived bone marrow CD34+ cells and CML K562 cells with lentiviral vectors containing FOLR3 SNP, FOLR3 SNP shRNA, and wild type FOLR3. The result indicated that FOLR3 SNP significantly promoted the clonogenicity of CD34+/K562 cells, while loss of FOLR3 SNP hindered cell differentiation (Figure 1B and D are data of CD34, Figure 1C and E are data of K562). K562 subcutaneous tumor formation in balb/c node mice confirmed that tumors weight and volume of FOLR3 SNP shRNA group were higher than control. While, small animal PET scanning showed that maximum standardized uptake value (SUVmax) of 18F-FDG of FOLR3 SNP+ group was higher than the rest. Experiments in vivo and vitro synergistically proved FOLR3 SNP promoted tumor cell differentiation, delayed tumor growth.To better understand how FOLR3 SNP promote tumor cell differentiation and delay tumor growth, we performed second transcriptome analysis. Consistently, both in FOLR3 SNP+ CD34+ and K562 cells, enrichment analysis revealed that differentially expressed genes were enriched in mitochondria associated Gene Ontology (GO) biological process (Figure F), in which mitochondria complex V matched genes were most significant, such as ATP5 family. In vitro, we demonstrated that ATP syntheses, maximal respiration and spare respiratory capacity of FOLR3 SNP+ CD34+/K562 cells were significantly higher than control and shFOLR3 counterpart through seahorse XF cell mito stress test (Figure G and H refer to CD34 and K562, separately). Electron microscope also exhibited an increase of mitochondrial in FOLR3 SNP+ cells.Mitochondria play an essential role in energy generation, cell signalling, differentiation, death and senescence in eukaryotic cells. We detected a series of genes related to aging, cell cycle and mitochondria unfolded protein response. The results showed that cell cycle kinase such as CDK4 decreased in FOLR3 SNP+ CD34+/K562 cells. On the other hand, senescence associated genes seemed increased. In conclusion, we highlighted the connection of FOLR3 and post-cessation relapse. FOLR3 SNP could be an indicator of TFR. Its internal mechanism might be the mitochondrion activation induced aging of residual leukemia cells. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Comparative Monitoring of Minimal Residual Disease (MRD) By RT-Quantitative (RT-qPCR) and Digital PCR (dPCR) in Ph+ Chronic Myeloid Leukemia (CML) Patients Treated with TKIs for Recognition of Stable Deep Molecular Response (DMR) and Identification of Best Candidates to TKIs Treatment Discontinuation

Current therapy of CML with tyrosine kinase inhibitors (TKIs) aims to achieve a Major Molecular Response to avoid the disease progression to blastic phase and, possibly, a Deep Molecular Response (DMR), to gain the opportunity for TKIs discontinuation and Treatment Free Remission (TFR). However, TFR strategies are not yet optimized, as well as the criteria for patients (pts) selection to TKI discontinuation are not well defined. The patient9s CML prognostic score, the duration of TKI treatment and "stable" DMR before discontinuation and the levels of DMR are still matters of debate. Due to its intrinsic limitations, RT-qPCR cannot be considered as an optimal tool for a precise detection of minimal BCR-ABL1 transcript levels and DMR monitoring. The digital PCR (dPCR) has emerged as a more sensitive and accurate method to detect and monitor the BCR-ABL1 minimal residual disease (MRD). This study focused on the BCR-ABL1 RT-q/dPCR comparative monitoring in CML pts treated with TKIs and with durable DMR (≥ 2 years), as conventionally assessed by RT-qPCR, before the enrollment. The aim was to evaluate the reliability and the efficiency of dPCR, as compared to RT-qPCR, for a better identification of "stable" DMR and for a better selection of the candidates for treatment discontinuation. 118 CML pts with durable DMR were enrolled and 493 peripheral blood samples were comparatively analyzed by both RT-qPCR, according to the last International Guidelines, and dPCR (QS3D Digital PCR System). RT-qPCR results were assessed as BCR-ABL1 %IS. dPCR results were assessed as number of BCR-ABL1 copies/□l of reaction and the molecular response was categorized as □ 0.468 or Starting from the first RTq/dPCR comparative assessment, the 118 pts were monitored every 3/4 months for at least 3 time points. Grouping the 118 pts according to the RT-qPCR molecular results at the enrolment, 50 cases (42%) resulted in the MR4.0group and 68 (58%) in the MR 4.5-MR5.0 group. No significant differences were observed between these 2 groups in terms of clinical and hematological characteristics. At the same time, the 118 pts were divided in 2 groups based on the comparative dPCR molecular results, according to the above mentioned cut-off value: 29 (25%) and 89 (75%) cases had dPCR values □ and □0.468 BCR-ABL1 copies/□l, respectively. No significant clinical differences were observed between these 2 groups. Out of these 118 pts, 87 (74%) discontinued the TKI treatment and 24 (28%) of them lost the DMR after a median time of 3 months (range 1-30). Based on dPCR, 23/87 (26%) and 64/87 (74%) had dPCR □ 0.468 and In order to reach a better recognition of stable DMR, which is strictly related with the probability to achieve and maintain TFR after TKIs discontinuation, we comparatively analyzed, by RTq/dPCR, the course of MRD during the follow up period. In the case of monitoring by RT-qPCR, a wide oscillation of the molecular responses was observed and they tended to be superimposable both in the group of pts with MR4.0 and in those with MR4.5 and 5.0. In the case of monitoring by dPCR, the values assessed at the enrolment and during the follow up revealed the capability of the dPCR to measure different and heterogeneous numbers of BCR-ABL1 copies in each pts. Moreover, the pts with a dPCR below the cut-off value of 0.468, at enrolment, were maintaining values (median 0,175; range 0-1,863), significantly lower (p This retrospective study show that the dPCR is more accurate and sensitive than conventional RT-qPCR for detecting and monitoring the BCR-ABL1 molecular levels and potentially able to improve the recognition of the stable DMR and selection of the candidates to TKI treatment discontinuation. Disclosures Bonifacio:Incyte: Consultancy; Pfizer: Consultancy; Amgen: Consultancy; Novartis: Research Funding; Bristol Myers Squibb: Consultancy. Gaidano:Morphosys: Honoraria; Amgen: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Gilead: Consultancy, Honoraria; Roche: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria. Rossi:Teva: Membership on an entity9s Board of Directors or advisory committees; Mundipharma: Honoraria; Sanofi: Membership on an entity9s Board of Directors or advisory committees; Janssen: Membership on an entity9s Board of Directors or advisory committees; Celgene: Membership on an entity9s Board of Directors or advisory committees; Abbvie: Membership on an entity9s Board of Directors or advisory committees; Pfizer: Membership on an entity9s Board of Directors or advisory committees; Novartis: Honoraria; Gilead: Membership on an entity9s Board of Directors or advisory committees; Sandoz: Honoraria; Jazz: Membership on an entity9s Board of Directors or advisory committees; Roche: Membership on an entity9s Board of Directors or advisory committees; BMS: Honoraria; Amgen: Membership on an entity9s Board of Directors or advisory committees. Gobbi:Novartis: Consultancy; Ariad: Membership on an entity9s Board of Directors or advisory committees; Pfister: Membership on an entity9s Board of Directors or advisory committees; Amgen: Consultancy; Janssen: Consultancy; Celgene: Membership on an entity9s Board of Directors or advisory committees. Voso:Celgene: Research Funding, Speakers Bureau. Abruzzese:Ariad: Consultancy; BMS: Consultancy; Novartis: Consultancy; Pfizer: Consultancy.

Feasibility of treatment discontinuation in chronic myeloid leukemia in clinical practice: results from a nationwide series of 236 patients

Over half of chronic myeloid leukemia (CML) patients in deep molecular response do not lose the major molecular response (MMR) after stopping treatment with tyrosine kinase inhibitors (TKI). This strategy is safe in clinical trials, but its applicability in the real-life setting remains unsettled. We describe the outcomes after TKI discontinuation in a nationwide series of 236 CML patients. Median follow-up from treatment discontinuation was 21.5 months and 5 patients died from CML-unrelated causes. TKI therapy was reinitiated due to MMR loss (n = 52), increase ≥ 1 log in BCR-ABL transcript level without losing MMR (n = 12), patient preference (n = 2), and withdrawal syndrome (n = 1). Treatment-free remission rate at 4 years was 64% (95% confidence interval, CI: 55%–72%). Cumulative incidence of molecular recurrence at 3 years was 33% (95% CI: 26%–38%). TKI treatment for < 5 years and MR4.5 duration shorter than 4 years were both associated with higher incidence of molecular recurrence. No patient had disease progression. 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). A significant increase in Hb and cholesterol levels was observed after imatinib withdrawal. Our results demonstrate that TKI treatment discontinuation is feasible in real-life clinical practice.

PKPD modeling of acquired resistance to anti-cancer drug treatment

Non-small cell lung cancer (NSCLC) patients greatly benefit from the treatment with tyrosine kinase inhibitors (TKIs) targeting the epidermal growth factor receptor (EGFR). However, emergence of acquired resistance inevitable occurs after long-term treatment in most patients and limits clinical improvement. In the present study, resistance to drug treatment in patient-derived NSCLC xenograft mice was assessed and modeling and simulation was applied to understand the dynamics of drug resistance as a basis to explore more beneficial drug regimen. Two semi-mechanistic models were fitted to tumor growth inhibition profiles during and after treatment with erlotinib or gefitinib. The base model proposes that as a result of drug treatment, tumor cells stop proliferating and undergo several stages of damage before they eventually die. The acquired resistance model adds a resistance term to the base model which assumes that resistant cells are emerging from the pool of damaged tumor cells. As a result, tumor cells sensitive to drug treatment will either die or be converted to a drug resistant cell population which is proliferating at a slower growth rate as compared to the sensitive cells. The observed tumor growth profiles were better described by the resistance model and emergence of resistance was concluded. In simulation studies, the selection of resistant cells was explored as well as the time-variant fraction of resistant over sensitive cells. The proposed model provides insight into the dynamic processes of emerging resistance. It predicts tumor regrowth during treatment driven by the selection of resistant cells and explains why faster tumor regrowth may occur after discontinuation of TKI treatment. Finally, it is shown how the semi-mechanistic model can be used to explore different scenarios and to identify optimal treatment schedules in clinical trials.

Molecular mechanisms in the resistance of CML stem cells to tyrosine kinase inhibitors and novel targets for achieving a cure

Tyrosine kinase inhibitors (TKIs) have dramatically improved the clinical outcomes of patients with chronic myeloid leukemia (CML) in the chronic phase. However, even if these patients achieve and maintain marked molecular responses such as a complete molecular response (BCR-ABL/ABL≤0.032% by international scale), discontinuation of TKI treatment results in early molecular relapse in most cases. Although several factors such as the Sokal score and the duration of TKI treatment have been identified as being related to treatment-free remission (TFR), identification of more definite factors or clinical conditions that would enable us to select patients who can maintain TFR is required. Relapse after TKI discontinuation is considered to be attributable to CML stem cells surviving even in patients who maintain marked molecular responses. A number of in vitro experiments have shown that TKI by itself cannot kill CML stem cells. Also, CML stem cells are resistant to TKI in a manner dependent on self-renewal factors (Hh, Wnt/β-catenin), cell cycle regulators (PML), metabotropic factors (FOXO3, Alox5), and adhesion molecules (CXCR4). In addition, surface markers specific for CML stem cells such as IL-1RAP and CD26 have been identified. New therapeutic strategies targeting these molecules in combination with TKI hold promise of achieving a more effective strategy for curing CML.

Discontinuation of tyrosine kinase inhibitors in chronic myeloid leukemia patients - worldwide battlefield.

Advances in understanding the pathogenesis of chronic myeloid leukemia (CML) and implementation of the therapy with tyrosine kinase inhibitors (TKI) could be considered as aprototype of successful fight against cancer. However, for an optimally responding patient it is recommended to follow the TKI therapy indefinitely. The question about the possibility of safe TKI treatment discontinuation in certain clinical situations was raised and is currently under close investigation worldwide. Currently, imatinib discontinuation trails have shown that about 60% of eligible patients experienced molecular recurrence within 6 months of treatment discontinuation, while the remaining 40% remained in defined deep molecular response throughout the duration of mostly two years follow-up. Interestingly, retreatment with the same TKI or another TKI was successful in the vast majority of patients demonstrating molecular recurrence of the disease. These findings support the concept of safe TKI treatment discontinuation and its usefulness for aspecific subset of CML patients. However, recent data are not sufficient for TKI discontinuation attempts outside clinical trials yet. Because of the high risk of potentially problematic molecular recurrences of the pathological clones, the key question is to find the right predictive marker of TKI discontinuation success, however it stays unsolved yet. This minireview brings aconcise summary of this hot topic with arealistic view from clinical routine. tyrosine kinase inhibitors, imatinib, discontinuation, chronic myeloid leukemia.

Treatment Cessation in Chronic Myeloid Leukemia As a Part of Treatment Process: Toxicity Determined and Active Stop of Tyrosine Kinase Inhibitors

Background: Clinical trials demonstrate a safe discontinuation possibility of tyrosine kinase inhibitors (TKI) in patients with deep molecular response (MR). However reasons and indications for TKI cessation as a part of treatment process have not been studied.Aims: To evaluate the eligibility of long term TKI cessation in CML patients with deep and long lasting MR. To describe the reasons of stopping therapy, principles and terms of observation without treatment, preserving and restoring of MR.Methods: We summarized retrospectively and prospectively 25 TKI discontinuation cases in 2 clinics of Russian Federation (Moscow, St.Petersburg, 2008-2014). Inclusion criteria were: 1) Ph+CML 2) MR4 (BCR-ABL<0,01%) for >12 months confirmed by >2 consecutive analyses 3) discontinuation of TKI treatment. Chronic phase (CP)/accelerated phase (AP) at diagnosis was 24/1. Sokal score for CP patients was 15/8/1 for low/intermediate/high risl group. Therapy before discontinuation was the following: imatinib 1st line (n=16), 2nd generation TKI (TKI2) 2nd-3rd line (n=9): 5 dasatinib/ 4 nilotinib. Me TKI duration was 7,2 (range 2,5-13) years, Me MR4 duration was 50 (range 12-97) months. IFN before TKI was received by 13(52%) of 25 patients for Me 18 months (2-60 months).Results: We specify 2 reasons of TKI discontinuation: 1) adverse events (AE) of TKI (Toxicity Group), n=18 2) self decision of patients (Active Group), n=7 (Table 1).Table 1Characteristics of CML patients according to reason of stopping TKI (n=25)Toxicity Group (n=18)Active Group (n=7)Ме of age, years (min-max)55 (27-74)36 (23-58)Ratio male/female (m:f)9m:9f3m:4fМе duration of TKI therapy, years (min-max)5,9 (2,5-13)8,6 (4,4-10,1)Ме duration of МО4 at treatment cessation, months (min-max)41 (12-97)67 (33-79)In Toxicity Group therapy was stopped for 1) AE grade 1-3 in 5 of 18 patients: unstable angina (2), hepatotoxicity (1), acute renal failure (1), menstrual dysfunction and infections (1); 2) AE grade 1-2 in 13 of 18 patients including recurrent or long lasting: fatigue, edema, arthralgia, muscle cramps, diarrhea, recurrent pleural effusion. The key clinical decision was not to restart TKI after AE termination and to continue monitoring of BCR-ABL transcript levels by RQ-PCR. For Active Group self-made discontinuation was in 7 patients with long lasting MR4 due to knowledge of safe discontinuation (4) and for conception (3). In 6 of 7 patients BCR-ABL monitoring was performed, 1 patient refused from monitoring.Treatment was restarted at major molecular response (MMR) loss (BCR-ABL>0,1%) or by decision of physician. In case of severe AE the patients were switched to alternative TKI.Thirteen (52%) of 25 patients were observed without treatment for Me 23 months (6-77 months), in 12 MR4 was maintained, 1 patient being off treatment for 54 months refused from monitoring (Active Group). Therapy was resumed in 10 patients with MMR loss and in 2 without MMR loss, by physician decision. All MMR loss cases occurred within first 6 months, no CML progression observed. Response restoration to MR4 was in 8 of 10 patients in 3-16 months, in other 2 it is early to estimateSummary/Conclusion: Observation without therapy may become an option in CML patients with mostly low/intermediate Sokal risk group, stable MR4 and recurrent/severe TKI toxicity. Self declared decisions of young patients with durable deep MR should be accompanied by regular RQ-PCR especially within first 6 months after TKI discontinuation. Resuming therapy at MMR loss shows to be safe. DisclosuresNo relevant conflicts of interest to declare.

Upregulation of Osteoactivin Upon Exposure to Tyrosine Kinase Inhibitors Impairs the T Cell Stimulatory Capacity of Monocyte-Derived Dendritic Cells

Abstract 1112▪▪This icon denotes a clinically relevant abstractTargeted therapies using tyrosine kinase (TK) inhibitors have significantly improved the treatment of cancer patients. Imatinib (Glivec, Gleevec, STI 571) was the first TK inhibitor (TKI) established for the treatment of cancer and efficiently blocks the activity of c-ABL, a non-receptor TK which is pathologically activated in philadelphia chromosome-positive (Ph+) chronic myelogenous leukemia (CML). Nilotinib (Tasigna) and dasatinib (Sprycel) are second-generation TKI that have shown efficacy in the treatment of Ph+ CML resistant or intolerant to imatinib. However, molecularly detectable disease persists in the majority of patients treated with TKI, causing relapse after discontinuation of TKI treatment in many cases. Thus, multiple approaches presently aim to combine TKI treatment with immunotherapy. As TKI, besides targeting their eponymous enzyme, influence multiple other signaling pathways involved in cellular functions, analysis of potential effects of TKI on immune effector cells may be key to develop successful combinatorial strategies. Due to their unique ability to initiate powerful anti-tumor T cell responses, dendritic cells (DC) are employed in many immunotherapeutic strategies aiming to eradicate the malignant cell population. Upon activation they change their expression pattern of cell surface molecules and secreted cytokines/chemokines, a process called DC maturation. Osteoactivin, also known as transmembrane glycoprotein NMB (GPNMB) and dendritic cell-associated transmembrane protein (DC-HIL), is a type I transmembrane glycoprotein that is detected abundantly in DC but not or substantially less in monocytes. Its expression can inhibit T cell activation by binding the type 1 transmembrane proteoglycan syndecan-4 (SD-4) on T cells. Here we extend our findings that the exposure of human peripheral blood monocytes to the immunosuppressive and anti-inflammatory cytokine IL-10 or to therapeutic concentrations of TKI during differentiation into monocyte-derived DC (moDC) leads to significant upregulation of osteoactivin at the transcript and protein level in vitro (Blood 2010 116: abstract 1733). We analyzed the expression of other inhibitory receptors, such as PD-L1, PD-L2, CD80, or CD86 and observed no significant differences of the expression under TKI treatment. Furthermore, we thoroughly examined the expression of osteoactivin in the presence of relevant maturation signals such as TLR ligands, IFN-γ or TNF. LPS, Poly I:C, Pam3Cys or R848 nearly abolished osteoactivin expression compared to untreated control cells. In contrast, IFN-γ or TNF did not significantly reduce osteoactivin expression below the basal level. To evaluate the involvement of osteoactivin in TKI-triggered effects on moDC function we performed mixed lymphocyte reactions with allogenic T cells. Osteoactivin upregulation upon exposure to imatinib, dasatinib and nilotinib resulted in significantly reduced T cell stimulatory capacity of moDC. This was not due to IL-10 upregulation but rather due to direct inhibitory effects of osteoactivin on T cell proliferation which could be overcome by addition of blocking anti-osteoactivin antibody. Our data demonstrate that upregulation of osteoactivin upon exposure of immature moDC to TKI is critically involved in the inhibition of DC function. These findings indicate that inhibition of osteoactivin expression or function may serve as a novel strategy in combinatory approaches using TKI and DC-based immunotherapy and may enhance the efficacy of immunotherapeutic interventions in cancer patients. Disclosures:No relevant conflicts of interest to declare.