Spillover effects of Medicaid expansion on insurance coverage, diagnosis, and survival among low-income elderly patients with cancer.

1522 Background: Medicaid expansion under the Affordable Care Act is associated with increased health insurance coverage and improved outcomes among patients with cancer < 65 years. Although not the target population, individuals ≥65 years may also benefit from Medicaid expansion through “welcome mat” effects, referring to the indirect increase in Medicaid enrollment from increased public awareness and streamlined enrollment procedures. This study examines the associations of Medicaid expansion with Medicaid coverage, stage at diagnosis, and survival among cancer patients ≥65 years. Methods: Using the National Cancer Database, we identified patients ≥65 years newly diagnosed with cancer between 2010-2022 residing in areas with median household income below 200% of the federal poverty level. We applied a quasi-experimental difference-in-differences design, with multivariable linear probability models to compare the changes in the percentage of dual-eligible or Medicaid-only coverage, stage at diagnosis, and two-year survival post (vs. pre) Medicaid expansion in expansion states compared with non-expansion states. Results: A total of 1,468,116 patients with cancer were identified, with 885,671 patients from expansion states and 582,445 patients from non-expansion states. After adjusting for sociodemographic characteristics, the percentage of patients with dual or Medicaid-only coverage increased from 10.27% to 11.33% in expansion states and decreased from 9.4% to 8.11% in non-expansion states, resulting in a net increase of 1.34 percentage points (ppt, 95% confidence interval [CI]: 1.12, 1.56) associated with Medicaid expansion. Differences were more pronounced among patients with stage III-IV cancers, females, non-Hispanic Black, metropolitan residents, and those with ≥2 comorbidities. The percentage of early-stage (I/II) cancer diagnoses decreased more in non-expansion states (49.82% to 47.19%) than in expansion states (47.63% to 46.06%), resulting in a net increase of 0.96 ppt (95% CI: 0.58, 1.34). The protective effects of Medicaid expansion were stronger for late-stage (III/IV) non-small cell lung and uterine cancers, as well as early-stage thyroid and bladder cancers. Two-year overall survival rates increased from 58.86% to 62.39% in expansion states and from 59.18% to 62.55% in non-expansion states, leading to a net increase of 0.95 ppt (95% CI: 0.61, 1.29). Improvements were most notable for prostate, lung, kidney, and bladder cancers. Conclusions: Medicaid expansion was associated with an increase in Medicaid coverage, early-stage cancer diagnoses, and improved two-year survival among patients diagnosed with cancer ≥65 years. Findings underscore the spillover benefits of Medicaid expansion in supporting low-income elderly populations and the importance of indirect benefits when evaluating Medicaid expansion’s broader impact.