Abstract
Background
Medicaid expansion under the Affordable Care Act has been associated with improved colorectal cancer (CRC) outcomes, predominantly attributed to earlier diagnosis and stage migration. However, it remains unclear whether survival benefits vary across disease stages.
Objective
To evaluate cancer-specific survival (CSS) after Medicaid expansion across disease stages among working-age adults with CRC, comparing the expansion state of California with the non-expansion state of Texas.
Methods
We conducted a retrospective cohort study using Surveillance, Epidemiology, and End Results (SEER) registry data (2007-2021) for patients aged 18-64 years with primary CRC. A difference-in-differences design compared pre-ACA (2007-2013) and post-ACA (2015-2021) periods between California and Texas. CSS was modeled using Cox proportional hazards regression adjusting for demographics, tumor characteristics, and treatments. Analyses were stratified by disease stage (localized, regional, distant) and race/ethnicity.
Results
Among 122,543 patients, CSS improved after Medicaid expansion in California relative to Texas. Stage-stratified difference-in-differences models showed a modest reduction in cancer-specific mortality for localized disease 0.985 (0.974-0.996), a larger reduction for regional disease 0.941 (0.900-0.983), and the greatest reduction for distant metastatic disease 0.689 (0.525-0.903). Improvements were consistent across racial/ethnic groups, with the largest relative reduction among non-Hispanic Black patients 0.855 (0.763-0.958).
Conclusion
Medicaid expansion was associated with stage-dependent improvements in CRC survival, with the most pronounced benefit for patients with metastatic disease. These findings suggest that enhanced access to systemic therapy, multidisciplinary care, and financial protection may yield survival gains beyond those mediated by stage shift alone.
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