Comparing nilotinib with dasatinib as second-line therapies in patients with chronic myelogenous leukemia resistant or intolerant to imatinib -- a retrospective chart review analysis.

Introduction: This study compared progression, progression-free survival (PFS), overall survival (OS), and treatment changes among chronic myelogenous leukemia patients in chronic phase (CML-CP) receiving nilotinib or dasatinib as second-line therapy.
Patients and Methods: Information on CML-CP patients switched from imatinib to nilotinib or dasatinib as second-line therapy was collected retrospectively from 122 US hematologists and oncologists through an online medical chart review. Progression, PFS, and OS were compared using multivariate Cox proportional hazard models, and treatment changes using chi-square tests.
Results: Of 597 imatinib resistant or intolerant patients, 301 initiated nilotinib and 296 dasatinib as second-line therapy. Nilotinib was associated with a lower risk of progression (hazard ratio [HR] = 0.27; p = 0.021) and longer PFS (HR = 0.48; p = 0.030) than dasatinib, with a median follow-up time of 11 months for nilotinib and 10 months for dasatinib. Nilotinib patients had a lower estimated hazard of mortality than dasatinib patients, though not statistically significant (HR = 0.46; p = 0.067). When treatment changes were classified by the physicians' justifications, fewer nilotinib patients had treatment changes due to ineffectiveness (2.0% vs. 5.1%, p = 0.041) or drug holidays due to intolerance (0.0% vs. 1.7%, p = 0.024) than dasatinib patients.
Conclusions: Among CML-CP patients in this retrospective chart review who switched from imatinib to either nilotinib or dasatinib, nilotinib was associated with a significantly lower risk of progression and longer PFS than dasatinib. Nilotinib patients were also less likely than dasatinib patients to subsequently have treatment changes due to ineffectiveness or drug holidays due to intolerance. These findings could be subject to unobserved confounders.