Discontinuation of tyrosine kinase inhibitors in chronic phase chronic myeloid leukemia is feasible in clinical practice based on recently published international recommendations. Nevertheless, predictive factors of molecular recurrence are not fully elucidated and long term follow-up of patients enrolled in clinical studies are required in order to update knowledge on discontinuation attempts particularly in terms of the safety and durability of treatment-free remission (TFR). In the current study, we updated results from the STIM2 study in the light of the consensual criterion of Molecular Recurrence (MRec) reported in different international recommendations. One hundred and eight patients lost MMR among the 199 patients included in the per protocol study. TFR probability was 43.4% [36.3-50.4] at 5 years, 40.9% [32.8-47.3] at 7 years and 34.5% [25.6-43.3] at 9 years with a median follow-up of 40.8 months (5.5-111 months). MRec occurred between 0 to 6 months, 6 to 24 months and after 24 months in 75 pts (69%), 15 pts (14%) and 18 pts (17%) respectively. Notably, the kinetics of MRec differed significantly between these 3 subgroups with a median time from loss of MR4 to MMR loss of 1, 7 and 22 months respectively. Predictive factors of MRec differed according to the time of occurrence of MRec. Imatinib treatment and deep molecular response durations and BCR::ABL1/ABL1 levels at TKI cessation as quantified by RT-ddPCR are involved in MRec occurring up to 24 months but not beyond. (ClinicalTrial.gov Identifier NCT#0134373).
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