High Cost Sharing and Specialty Drug Initiation under Medicare Part D: A Case Study in Newly Diagnosed Chronic Myeloid Leukemia Patients
Tyrosine kinase inhibitors (TKIs) have revolutionized the treatment of chronic myeloid leukemia (CML), making it an apt case study. Utilizing 2011-2013 100% Medicare claims, we examined rates of TKI initiation and time to initiation among fee-for-service Medicare Part D patients newly diagnosed with CML (captured via diagnostic and lab test codes and absence of previous TKI claims), as compared to their counterparts who were receiving low-income subsidies (LIS) and facing nominal cost sharing (≤$5). All TKIs were subject to 25%-33% coinsurance across all plans in our sample. Further, given median total costs of ~$6500 per 30-day TKI prescription, the first drug fill “straddled” Part D benefit phases, resulting in an out-of-pocket cost >$2500 for non-LIS patients. We found that non-LIS patients were less likely than LIS patients to have a TKI claim within 6 months of diagnosis (44.9% vs. 67.8%, p<0.05) and on average, took twice as long to fill one when they did (mean 50.1 vs. 23.9 days, p<0.05). Cox regressions controlling for sociodemographic, clinical (e.g., CML severity), and plan characteristics (e.g., utilization management tools) confirmed descriptive findings (HR=0.61, p=0.001). Sensitivity analyses using 6 alternate algorithms to identify new CML patients, and using different model specifications (i.e., plan ID fixed effects to ensure LIS and non-LIS patients were facing the same plan-level restrictions aside from cost sharing), and using a different definition of index date (i.e., using the second claim as the index date to count time to TKI initiation) showed consistent findings.
In summary, high cost sharing among non-LIS patients was associated with reduced and/or delayed access to TKIs under Part D. Although the Part D coverage gap will be phased out by 2020, 25%-33% specialty tier cost sharing will remain and may create financial barriers that inadvertently discourage use of cost-effective treatments.