Spillover effects of Medicaid expansion on insurance coverage among low-income older individuals newly diagnosed with cancer.

168 Background: Medicaid expansion is associated with increased insurance coverage and improved health outcomes among patients diagnosed with cancer < 65 years. Although not the target population, individuals ≥65 years may benefit from Medicaid expansion through “welcome mat” effects – the indirect increase in enrollment, particularly those with low income eligible for both Medicaid and Medicare (dual-eligible). This study aims to examine the associations of Medicaid expansion with Medicaid coverage, including both dual-eligible and Medicaid-only, among individuals diagnosed with cancer. Methods: Using the National Cancer Database, we identified patients ≥65 years newly diagnosed with cancer between 2010-2019 with income below 138% federal poverty level. We applied a quasi-experimental design, the difference-in-difference approach, with multivariable linear probability models to compare the changes in the percentage of dual-eligible or Medicaid-only coverage post (vs. pre) Medicaid expansion in expansion v. non-expansion states. Analyses were also stratified by key demographic characteristics. Results: A total of 256,997 patients with cancer were identified, with 136,373 patients from expansion states and 120,624 patients from non-expansion states. After adjusting for sociodemographic characteristics, the percentage of patients with dual or Medicaid-only coverage increased from 16.84 to 18.09 in expansion states and decreased from 14.14 to 12.62 in non-expansion states, resulting in a net increase of 2.11 percentage points (ppt, 95% confidence interval: 1.55, 2.67) associated with Medicaid expansion. Differences were more pronounced among patients diagnosed with stage III-IV cancers (DD: 2.53 ppt, 95%CI: 1.58, 3.48), racialized as non-Hispanic Black (DD: 3.71 ppt, 95%CI: 2.70, 4.73), residing in metropolitan areas (DD: 2.77 ppt, 95%CI: 2.08, 3.47), with two or more comorbidities (DD: 4.14 ppt, 95%CI: 2.47, 5.80), and treated in comprehensive (DD: 2.98 ppt, 95%CI: 2.02, 3.94) or academic cancer centers (DD: 3.31 ppt, 95%CI: 2.14, 4.49). Conclusions: Medicaid expansion was associated with an increase in Medicaid enrollment among patients diagnosed with cancer at 65 or older, suggesting spillover benefits of Medicaid expansion in supporting low-income elderly populations with cancer.