Purpose: Patients eligible for Medicare Part D low-income subsidy have lower cost-sharing for both IV and oral cancer therapies. We evaluated associations between low-income subsidy and treatment choice, treatment initiation, and overall survival in patients with metastatic prostate cancer.
Materials and methods: We identified men aged 66 years and older diagnosed with stage IV prostate cancer between 2010 and 2017 included in the Surveillance, Epidemiology, and End Results-Medicare linked data set. Using linear probability models, we evaluated the impact of low-income subsidy on type of first supplementary treatment (oral vs IV) among patients who received nonandrogen deprivation therapy supplementary systemic therapy, and initiation of any nonandrogen deprivation therapy supplementary systemic therapy. Overall survival was estimated with Kaplan-Meier curves.
Results: Of the 5,929 patients included, 1,766 (30%) had low-income subsidy. On multivariable analysis, those with low-income subsidy were more likely to receive oral as opposed to IV treatments compared to patients without low-income subsidy (probability difference: 17%, 95% CI 12, 22). However, patients with low-income subsidy were less likely to initiate any nonandrogen deprivation therapy supplementary systemic therapy (oral or IV) compared to those without low-income subsidy (probability difference: 7.9%, 95% CI 4.8-11). Additionally, patients with low-income subsidy experienced worse overall survival than those without low-income subsidy (P < .001).
Conclusions: While low-income subsidy was associated with increased use of more expensive oral therapies in men with metastatic prostate cancer, barriers to accessing these treatments still exist. These findings stress the importance of continued efforts to improve health care access to low-income individuals.
Keywords: Medicare Part B; Medicare Part D; androgen antagonists; financial stress; prostatic neoplasms.