P669: analysis of factors influencing the decision to stop tki treatment in cml patients in deep molecular response

Background: Stopping TKI treatment in patients with CML is getting more frequent but many questions remain unanswered. It is not even known the proportion of patients who do not actually want to stop the TKI treatment although they are in the long-term deep molecular response. Aims: To determine how many patients with CML in deep molecular response do not wish to stop TKI treatment. To explore any differences between the cohort of patients that agree and disagree with TKI stopping. To evaluate the reasons for the decision not to stop TKI treatment. Methods: In Czechia, by law, the care for adult CML patients is centralized into eight centres. All the centres collaborate within the Czech Leukemia Study Group for Life (CELL) and contribute to the detailed database of CML patients. The Czech nation-wide clinical trial HALF (ClinicalTrials.gov Identifier: NCT04147533), which started in June 2020, tests to stop TKIs in CML patients after the two-step dose reduction. The TKI stopping in the clinical trial HALF is being offered to all suitable CML patients in Czechia. An integral part of the clinical trial was the questionnaire Anti-HALF. All patients who did not want to enter the HALF project were asked to complete this questionnaire. Anti-HALF consists of 20 questions regarding sex, age, occupation, socioeconomic status, TKI therapy and its side effect, compliance, and finally, the reasons for decision not to stop the TKI. The project Anti-HALF was finished at the end of 2022, the HALF project continues. Results: In June 2020, the number of living patients with CML registered in CELL database was 1751. By the end of 2022, the stopping of TKI treatment was offered to 246 of them (14%/1751 pts); 190 of 246 pts (77.2%) were enrolled (HALF patients, H pts), 45 (18.3%) did not want to participate, but completed the Anti-HALF questionnaire (Anti-HALF patients, AH pts), and 11 (4.5%) refused even to complete the survey. There were 143 H pts vs. 36 AH pts on imatinib, 31 H pts vs. 9 AH pts on nilotinib, and 16 H pts vs. 0 AH pts on dasatinib. AH pts were more frequently of female sex (64.4% vs. 46.8%; p=0.046), elderly (median 67.5y vs. 61.8y; p =0.0342), more frequently retired or unemployed (75.6% vs. 54.5%; p=0.0171) and with already reduced dosing of imatinib (55.6% vs. 34.3%; p=0.0223). The factors which did not seem to play a role were the type of TKI and, unexpectedly, the presence of subjective side effects, or the average distance to travel to treating physician. The AH pts took longer their current TKI, but this difference had a borderline statistical significance (median 9.2y vs. 8.0y; p=0.0764). The AH pts were minimally or not stressed during the regular follow up (82.2%), they felt the TKI as effective and safe treatment (57.8%), were very compliant (80.0%), mostly without any subjective side effects of TKI (62.2%). The decision to enter or not the trial was rather difficult for AH pts (53.3%), with serious concern about the disease recurrence (62.2%) and less effective re-treatment (55.6%). Summary/Conclusion: Surprisingly, there is a high proportion of patients with CML who do not wish to stop TKI treatment despite fulfilling the generally accepted stopping criteria. We believe that this is clinically important and so far underexplored phenomenon deserving further study, and this fact has to be taken into the account when counselling the patients. Detailed data will be presented. Supported by the national budget through MEYS, RI CZECRIN (LM2018128) and from ERDF Project CZECRIN_4 PATIENTS (CZ.02.1.01/0.0/0.0/16_013/0001826) and by Ministry of Health of the Czech Republic, grant no. NU22-03-00136 and by National Institute for Cancer Research Project (Programme EXCELES, ID Project No. LX22NPO5102) - Funded by the EuropeanUnion - Next Generation EU. Keywords: Tyrosine kinase inhibitor, treatment-free remission, Chronic myeloid leukemia