Abstract B081: How patient cost sharing of tyrosine kinase inhibitors affects initiation, adherence, and outcomes in patients with newly diagnosed chronic myeloid leukemia: A retrospective claims-based study
Authors: Phuar Hsiao Ling , Begley Charles E. , Krause Trudy M. , Chan Wenyaw 
Published: August 2020

Background: High out-of-pocket costs may lead to disparities in the initiation of and subsequent adherence to expensive medications. For newly diagnosed chronic myeloid leukemia (CML) patients, early access to tyrosine kinase inhibitors (TKI) is a consistent predictor of adherence and optimal response. The study examines the association between TKI out-of-pocket costs, initiation, adherence, and total health care utilization and costs among patients who initiated TKI within 12 months following first CML diagnosis.

Methods: Individuals aged 18 to 64 with an initial diagnosis of CML were identified in the Truven Health MarketScan® Commercial Claims and Encounters database between 1/1/2011 and 12/31/2015. The association between cost sharing and TKI initiation was evaluated using Cox proportional hazards regression models applied to early (patients receiving therapy within 6 months of diagnosis) and late initiators (6-12 months after diagnosis). The association between initiation, adherence, utilization, and costs was examined in a subset of the sample with continuous enrollment for 12 months following TKI initiation. Adherence was estimated using the proportion of days covered (PDC), defined as the percentage of the proportion of days covered by the prescription fill during the 12-month follow-up period (adherent patients have PDC ≥80%). Health care utilization was compared using negative binomial regression models. Health care cost differences between early and late initiators were estimated using generalized linear models. All models were controlled for potential confounding factors.

Results: The study sample consisted of 624 patients, 607 (97.3%) early initiators and 17 late. Patients with late initiation had higher TKI out-of-pocket costs (≥75th percentile in the distribution of costs) for the initial 30-day supply (HR=0.83; p=0.047). Among 479 patients who were continuously enrolled during the 12-month follow-up period from TKI initiation, 472 (98.5%) initiated TKI within 6 months. Early initiators had a twofold increase in predicted PDC (75.4% vs. 36.2%; p&lt;0.001). Over the 12-month follow-up period, early initiators incurred $34,075 more in total annual health care costs (p=0.002); cost differences were mainly driven by a TKI pharmacy cost difference of $31,929 (p&lt;0.001). Late initiators were much more likely to have all-cause hospitalizations (IRR=5.94; p=0.026), or CML-specific hospitalizations (IRR=6.94; p=0.019).

Conclusions: Higher out-of-pocket costs for TKI may lead to delays in initiation and nonadherence. Patients with early initiation of TKI and adherence had lower nonmedication health care costs that were more than offset by higher TKI medication costs. Findings suggest that high drug out-of-pocket costs may limit access to life-saving oral cancer medications, causing disparities in TKI initiation and adherence for CML treatment. The timeliness of TKI initiation, however, was not shown to lead to overall cost savings during a 12-month follow-up period.

Citation Format: Hsiao Ling Phuar, Charles E. Begley, Trudy M. Krause, Wenyaw Chan. How patient cost sharing of tyrosine kinase inhibitors affects initiation, adherence, and outcomes in patients with newly diagnosed chronic myeloid leukemia: A retrospective claims-based study [abstract]. In: Proceedings of the Eleventh AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2018 Nov 2-5; New Orleans, LA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl):Abstract nr B081.