Clinical outcome of chronic myeloid leukemia patients who switch from first-line therapy with a second generation tyrosine kinase inhibitor to an alternative TKI

While second generation tyrosine kinase inhibitors (2GTKIs) are highly effective therapies for chronic myeloid leukemia (CML), a significant minority of patients who initiate a 2GTKI will require a switch to an alternative TKI. The long-term outcomes of those who require a change in therapy after front-line 2GTKI therapy are largely undescribed. Here we describe the clinical outcomes associated with switch to an alternative TKI after first-line therapy with a 2GTKI. Of 232 patients who initiated a 2GTKI during the study period, 76 (33 %) switched to an alternative TKI. Reasons for switching included intolerance (79 %) and resistance (21 %). Among the 60 patients who switched due to intolerance, 53 (88 %) were able to achieve or maintain a major molecular response (MMR) with 5-year progression-free survival (PFS) 90.5 % (95 % CI 90.4-90.6 %). Amongst the 16 patients who switched due to resistance, 8 patients (50 %) were able to achieve MMR with 5-year PFS 80.4 % (95 % CI 80.2-80.6 %). Most patients who switched due to intolerance remained on their second-line TKI. Approximately 25 % of patients who initiate first-line 2GTKI in a real world setting will ultimately switch to an alternate TKI due to intolerance. Patients who switch for intolerance continue to enjoy excellent clinical outcomes.