Study of imatinib treatment patterns and outcomes among US veteran patients with Philadelphia chromosome-positive chronic myeloid leukemia

This study investigated the treatment patterns and outcomes for US veteran patients with chronic myeloid leukemia-chronic phase (CML-CP) initiated on imatinib (IM). Patients (age≥18 years) with at least one CML diagnosis (International Classification of Diseases, Ninth Edition Clinical Modification: 205.1x) during the period January 1, 2000, to June 30, 2011, and initiated on IM as first-line therapy were identified in the VISN 16 data warehouse (N=137). Accelerated and blastic phases (AP/BP) were identified on the basis of WHO classification using complete blood count (CBC) data. Rates of IM dose adjustment, discontinuation, and switching to another drug therapy were estimated. Time to discontinuation, progression to AP/BP, and survival were assessed using Kaplan-Meier analysis (KM). During follow-up, 19.0% of patients had at least one dose increase; of these, 19.2% switched to another therapy. Dose reductions occurred in 25.6% of patients. Among patients who discontinued IM (n=74; 54.0%), whereas 16.2% switched to other therapies, 27.0% neither restarted IM nor switched to other therapies. KM showed that 25.6% and 42.4% of patients discontinued IM treatment by year 1 and 2, and 8.1% and 16.0% demonstrated disease progression by year 1 and 2, respectively. Among patients who experienced disease progression (n=28), 32.1% continued IM postprogression, 32.1% discontinued IM before progression, 28.6% discontinued IM postprogression without switching, and 7.1% switched to other therapies postprogression. The mortality rates were 3.0% and 9.5% after IM initiation, and 21.7% and 42.7% after disease progression by year 1 and 2, respectively. In this veteran population, a substantial number of IM-treated patients, including those with disease progression, either discontinued or interrupted IM use without switching to other therapies.