A retrospective analysis of therapy adherence in imatinib resistant or intolerant patients with chronic myeloid leukemia receiving nilotinib or dasatinib in a real-world setting

Objectives: To compare adherence to second-generation tyrosine kinase inhibitors (TKIs) dasatinib and nilotinib in patients with imatinib resistant or intolerant chronic myeloid leukemia (CML) receiving second-line therapies. Methods: Two U. S. administrative claims databases were reviewed (January 1997 to March 2011) for CML patients previously treated with imatinib, who received >= 1 prescription of dasatinib or nilotinib and had continuous enrollment >= 1 month before and after the index date (first dasatinib or nilotinib prescription date). Medication possession ratios (MPRs) and proportion of days covered (PDCs) were evaluated between the treatment initiation date until the end of continuous eligibility, for a maximum of 12 months. Sensitivity analyses were conducted to compare patients initiated on nilotinib to patients who initiated dasatinib 100 mg/day and 140 mg/day separately. This study provides updated results of a previously published study. Results: In total, 878 CML patients who received second-line treatment with either dasatinib (n = 550) or nilotinib (n = 328) were studied. Dasatinib users were less adherent compared to nilotinib users; mean MPR was 0.739 (standard deviation [SD] 0.246) for dasatinib and 0.800 (SD 0.246) for nilotinib (adjusted difference 0.061; P = 0.002). Subgroup analyses of patients who initiated dasatinib 100 mg/day and 140 mg/day separately presented similar trends; after multivariate adjustment, adherence was 0.039 points lower in the 100 mg/day group (P = 0.034) and 0.120 points lower in the 140 mg/day group (P<0.001). Conclusions: Among patients treated in the second-line CML setting, those treated with nilotinib had significantly higher adherence compared to patients treated with dasatinib, regardless of dasatinib dose (100 mg/day and 140 mg/day). Limitations: The study was subject to common limitations of claims data, which lack clinical information, may contain inaccuracies in diagnosis and procedure coding, and may not truly reflect actual drug consumption. Moreover, daily doses calculated based on refill records may not reflect accurate dosing regimens.