Racial and Ethnic Disparities Along the Treatment Cascade Among Medicare Fee-for-Service Beneficiaries With Metastatic Breast, Colorectal, Lung, and Prostate Cancers

PURPOSE This study evaluated racial and ethnic disparities along the treatment cascade for Medicare fee-for-service patients with metastatic breast, colorectal, lung, and prostate cancers and disparities in overall survival by treatment receipt and quantified factors contributing to these disparities. METHODS Medicare fee-for-service beneficiaries with newly diagnosed metastatic hormone receptor–positive/human epidermal growth factor receptor 2–negative breast, colorectal, non–small cell lung, and prostate cancers from the SEER-Medicare-linked database (2016-2020) were studied. We used multivariable logistic regression to evaluate disparities along the treatment cascade, multivariable Cox regressions to evaluate disparities in overall survival by treatment receipt, and Oaxaca-Blinder decomposition to quantify the contribution of factors related to disparities. RESULTS Of 18,652 White, 1,898 Black, and 1,465 Hispanic beneficiaries, within 2 months of diagnosis, 78% of patients were alive and 87% saw a medical oncologist—without consistent disparities. There were disparities in receiving any systemic therapy: breast (59% of Black patients received systemic therapy, 60% Hispanic, 68% White, P = .021), colorectal (23% Black, 31% Hispanic, 34% White, P < .001), lung (26% Black, 37% Hispanic, 39% White, P < .001), and prostate (56% Black, 76% Hispanic, 77% White, P < .001) cancers. For every cancer, <35% of patients received guideline-directed systemic therapy. After restricting to patients who received any systemic therapy within 2 months of diagnosis, overall survival disparities were no longer significant. Across all malignancies, low-income subsidy status—of which 87.6% was dual-eligible—contributed most to explaining disparities in treatment (20%-45% of the disparity). CONCLUSION Care delivery and policy interventions intended to narrow racial and ethnic overall survival disparities in Medicare patients with metastatic cancer should target disparities in not receiving first-line systemic therapy and address the unique needs of beneficiaries with low-income subsidy status or dual eligibility.