Real-world analysis of tyrosine kinase inhibitor treatment patterns among patients with chronic myeloid leukemia in the United States

Purpose: The treatment of chronic myeloid leukemia (CML) has improved considerably since the introduction of the tyrosine kinase inhibitor (TKI) imatinib in 2001 and the approval of second-generation TKIs (dasatinib and nilotinib) beginning in 2006.The objective of this study was to explore treatment patterns of TKI therapy (adherence, duration, and switching) among patients with CML in the United States, following the availability of second-generation TKIs.

Methods: This study used US health plan claims data from January 1, 2007, through December 31, 2011. Patients were required to be aged ≥18 years, have a prescription fill for a TKI, and a diagnosis of CML. Duration of TKI use was determined based on a gap in TKI coverage of ≥180 consecutive days after TKI initiation or switch to another TKI within the 180-day window. To account for censoring due to disenrollment from the health plan or end of the study period, median treatment duration was projected by using the Kaplan-Meier estimator.

Findings: We identified 695 patients who started TKI treatment and had a CML diagnosis during the study time frame. The mean age of patients was 55 years, and 58% of patients were male. The most common first-line TKI was imatinib (82%), with dasatinib and nilotinib use equally distributed (9%). Among the 148 (21.3%) patients who initiated a second-line TKI, the majority had switched from imatinib to dasatinib or nilotinib (86%). The median duration of first-line TKI use was 39.8 months and second-line TKI use was 22.4 months. Median duration of treatment for first-line (P = 0.4342) and second-line (P = 0.1792) treatment did not differ significantly according to TKI. Mean adherence (ie, proportion of days covered) during the first line of therapy was 0.90.

Implications: For the US patients studied, we found that imatinib was used more frequently than other TKIs in the first-line setting, but there was an increased use of second-generation TKIs in the first-line setting over time (9% in 2008 vs 43% in 2011 were nilotinib or dasatinib users). Only about one fifth of patients switched to a second-line TKI during the period of data collection.