Tyrosine Kinase Inhibitors and the Relationship With Adherence, Costs, and Health Care Utilization in Commercially Insured Patients With Newly Diagnosed Chronic Myeloid Leukemia: A Retrospective Claims-Based Study.

Objective: To examine the association among tyrosine kinase inhibitor (TKI) out-of-pocket costs, adherence, and health care costs and utilization in a large group of commercially insured patients with chronic myeloid leukemia (CML). Materials and Methods: Patients with CML aged 18 to 64 years were identified using IBM MarketScan Commercial Database between April 1, 2011 and December 31, 2014. Patients were required to be continuously enrolled 3 months before and 12 months after TKI (imatinib, dasatinib, or nilotinib) initiation. TKI adherence is estimated using the proportion of days covered (PDC), defined as the percentage of the PDC by the prescription fill during the 12-month study period (adherent patients have PDC >= 80%). Health care cost differences between adherent and nonadherent patients were estimated using generalized linear models. Health care utilization was compared using negative binomial regression models. All models were controlled for potential confounding factors. Results: The study sample consisted of 863 patients, where 355 (41.1%) patients were classified as adherent. Over the study period, nonadherent patients incurred US$10,974 more in medical costs (P<0.001), and US$1663 more in non-TKI pharmacy costs (P<0.01). Adherent patients incurred US$28,184 more in TKI pharmacy costs (P<0.001) that resulted in US$18,305 more in overall total health care costs (P<0.001). Adherent patients, however, were estimated to be less likely to have all-cause hospitalizations (incidence rate ratio, 0.32;P<0.001), or CML-specific hospitalizations (incidence rate ratio, 0.31;P<0.01). Conclusions: Patients with CML with better adherence experienced fewer hospitalizations, resulting in medical service cost savings. These lower medical costs, however, were more than offset by higher TKI medication costs observed during the first year of TKI therapy.