Identification of chronic myeloid leukemia patients treated with imatinib who are potentially eligible for treatment discontinuation by assessing real-life molecular responses on the international scale in a EUTOS-certified lab

A retrospective study was performed to describe molecular responses (MR) on the international scale (IS) in patients with chronic myeloid leukemia (CML) treated with imatinib in routine clinical practice in Belgium and to identify patients potentially eligible for treatment discontinuation. The analysis included 116 patients with CML in chronic phase at treatment centers sending blood samples for molecular follow-up to a single EUTOS-certified laboratory. IS MR from the last patient visit between October 2014 and April 2015 were retrospectively collected. Most patients (93.1%) had an IS MR corresponding to an optimal response per European LeukemiaNet 2013 guidelines; 53.4% (62/116) of patients were in deep molecular responses ≥MR4.5 at their last visit (mean treatment duration: 91.0 months) among whom 36.2% (42/116) had been receiving imatinib for >5.8 years and 26.7% (31/116) for >8 years (margins of error: 8.74% and 8.05%, respectively). These patients would likely have the highest chance of staying in treatment-free remission (TFR) upon discontinuation, based on published TFR trial data. Although our study only provides a snapshot in time of a patient's last MR reported, without precise information regarding MR duration, the study settings could nevertheless support the feasibility of attempting TFR outside clinical trials in the future.