HOW PATIENT COST SHARING AFFECTS TYROSINE KINASE INHIBITORS ADHERENCE AND OUTCOMES AMONG COMMERCIALLY INSURED PATIENTS WITH NEWLY DIAGNOSED CHRONIC MYELOID LEUKEMIA

Untreated chronic phase chronic myeloid leukemia (CML) will eventually progress to advanced phase in 3 to 5 years. Treating CML with tyrosine kinase inhibitors (TKIs) has turned it into a chronic, manageable disease where most patients experience near normal life expectancy, particularly those diagnosed before age 65 years. Patients are required to continuously take their oral TKIs daily to produce the anticipated benefit of long-term survival. High out-of-pocket costs may lead to disparities in the initiation of and subsequent adherence to these expensive TKIs. Therefore, the goal of this dissertation is to assess the relationship between patient prescription cost sharing, TKIs initiation and adherence, and healthcare utilization and costs in a large group of commercially insured patients with newly diagnosed CML. The objective is twofold: 1) determine how patient cost sharing of TKI affects initiation, and healthcare utilization and costs, and 2) examine the association between TKI out-of-pocket costs, adherence, and healthcare utilization and costs. For these two objectives, we conducted a retrospective cohort study using longitudinal medical and pharmacy claims data from IBM® MarketScan® Commercial Database from 2011 to 2015. We included patients who were recently diagnosed with CML and filled at least one prescription for TKI. We found that high out-of-pocket costs for TKI medications put patients at increased risk of non adherence. Patients with early initiation of TKI and better adherence had higher TKI medication costs, but experienced fewer hospitalizations, resulting in lower medical and total annual healthcare costs. In summary, our findings suggest that high drug out-of-pocket costs may limit access to life-saving oral anticancer medications, causing disparities in TKI initiation and adherence for CML treatment. Oral anticancer medications are typically covered under a pharmacy benefit with substantial out-of-pocket costs due at the time the medication is obtained at the pharmacy. Efforts to lower drug prices and subsequently, the out-of-pocket costs for TKI medications could significantly improve adherence, and overall health and economic outcomes among CML patients