High cost sharing and specialty drug initiation under Medicare Part D: a case study in patients with newly diagnosed chronic myeloid leukemia.

OBJECTIVES Specialty drugs often offer medical advances but are frequently subject to high cost sharing. This is particularly true with Medicare Part D, where after meeting a deductible, patients without low-income subsidies (non-LIS) typically face 25% to 33% coinsurance (initial coverage phase with "specialty tier" cost sharing), followed by ~50% coinsurance (coverage gap phase), and then 5% coinsurance (catastrophic phase). Yet, no studies have examined the impact of such high cost sharing on specialty drug initiation under Part D. Oral tyrosine kinase inhibitors (TKIs) have revolutionized the treatment of chronic myeloid leukemia (CML), making it an apt case study. STUDY DESIGN A retrospective claims-based analysis utilizing 2011 to 2013 100% Medicare claims. METHODS TKI initiation rates and time to initiation were compared between fee-for-service non-LIS Part D patients newly diagnosed with CML and their LIS counterparts who faced nominal cost sharing of ≤ $5. RESULTS The first 30-day TKI fill "straddled" benefit phases, for a mean out-of-pocket cost of $2600 or more for non-LIS patients. Non-LIS patients were less likely than LIS patients to have a TKI claim within 6 months of diagnosis (45.3% vs 66.9%; P < .001) and those initiating a TKI took twice as long to fill it (mean = 50.9 vs 23.7 days; P < .001). Cox regressions controlling for sociodemographic, clinical, and plan characteristics confirmed descriptive findings (hazard ratio, 0.59; 95% CI, 0.45-0.76). Extensive sensitivity analyses confirmed the robustness of our findings. CONCLUSIONS High cost sharing was associated with reduced and/or delayed initiation of TKIs. We discuss policy strategies to reduce current financial barriers that adversely impact access to critical therapies under Medicare Part D.