Medicaid Expansion and Mortality Reduction in Women with Ovarian Cancer: A Population-Based Cohort Study

Objective: To evaluate the impact of Medicaid expansion under the Affordable Care Act (ACA) on overall mortality among women diagnosed with ovarian cancer and to assess whether the benefits varied by race/ethnicity and neighborhood income level. Design: Retrospective, population-based cohort study using a difference-in-differences approach with Cox proportional hazards modeling. Setting: Statewide cancer registry data from the United States, 2005 to 2022. Population: A total of 88,024 women aged 40–64 years diagnosed with primary ovarian cancer. Methods: States were categorized as early Medicaid expansion (implemented by 2014) or non-expansion. Adjusted hazard differences were estimated to assess the association between Medicaid expansion and overall mortality. Subgroup and three-way interaction analyses examined disparities by race/ethnicity and ZIP code–level income. Main Outcome Measures: Overall mortality measured as adjusted differences in log hazard ratios pre- and post-expansion. Results: We analyzed a cohort of 88,024 women aged 40–64 years diagnosed with ovarian cancer between 2005 and 2022 Of these, 44,608 (50.7%) were diagnosed before Medicaid expansion and 43,416 (49.3%) after. In expansion states, the proportion of Medicaid beneficiaries increased from 10.2% pre-expansion to 18.0% post-expansion. In contrast, non-expansion states showed only a modest increase (8.2% to 9.0%). Expansion states also saw a sharp decline in the uninsured rate, dropping from 6.3% to 2.5%, while non-expansion states experienced only a minor change (11.2% to 10.2%). Medicaid expansion was associated with a 38.0% reduction in overall mortality compared to non-expansion states [DID]: -0.380, 95% CI: –0.647 to –0.114; p=0.005).Conclusions: Medicaid expansion was associated with increased Medicaid coverage, reduced uninsured rates, and a significant reduction in overall mortality among women with ovarian cancer in the United States.