Response to Tyrosine Kinase Inhibitors in Real-World Patients With Chronic Myeloid Leukemia

Background: Tyrosine kinase inhibitors (TKIs) are the front-line therapy for chronic myeloid leukemia (CML), where phase 3 clinical trials have demonstrated their safety and efficacy. However, trial patients may not be representative of real-world patients (RWPs). Objective: To evaluate RWP clinical factors associated with effectiveness and safety in CML patients treated with TKIs. Methods: Patients with CML treated with at least 30 days of imatinib, dasatinib, nilotinib, or bosutinib between 2014 and 2018 were included. Patients were stratified into categories based on the number of factors that would have precluded enrollment into pivotal TKI phase 3 trials (0, 1, ≥2). End points included complete hematologic response (CHR), early molecular response (EMR), major molecular response (MMR), adverse event (AE)-induced dose decreases, treatment interruptions, and treatment discontinuations. Results: Final analyses included 174 patients. Patients with ≥2 factors had a higher risk of dose decreases (relative risk = 1.54; 95% CI = 1.02-2.34; P = 0.02) and a shorter time to dose decrease (hazard ratio = 2.43; 95% CI = 1.23-4.97; P = 0.006) compared with patients with 0 factors. Significant differences were observed in CHR at 1 month and MMR at 3 months between patients with 0 and ≥2 factors ( P = 0.03 and P = 0.04, respectively). Conclusion and Relevance: Approximately 60% of our RWPs would have been excluded from the pivotal phase 3 TKI trials. These data suggest that RWPs require more precise dosing to achieve CML clinical milestones and to mitigate AEs, but findings should be validated prospectively.