Association of Medicaid expansion with pre-diagnosis coverage continuity and 2-year overall survival in pediatric patients with blood cancer.

11033 Background: Continuous insurance coverage is critical for timely cancer diagnosis and treatment, yet many patients gain Medicaid only around the time of diagnosis. Although the Affordable Care Act Medicaid expansion targeted adults, it may indirectly influence children via a “welcome mat” effect by increasing outreach and boosting uptake among families with eligible children. The extent to which state expansion status influences Medicaid coverage continuity and survival among Medicaid-insured children with blood cancers—conditions lacking routine screening and often with acute presentation—remains unclear. Methods: Using linked SEER-Medicaid data, we identified 7,536 patients age ≤21 newly diagnosed with leukemia or lymphoma between 2009-2019 who had ≥1 month of Medicaid enrollment from 12 months pre-diagnosis through two months post-diagnosis. Coverage patterns were categorized as: 1) continuous Medicaid (12-13 months enrolled pre-/peri-diagnosis), 2) newly gained Medicaid (enrollment starting at diagnosis or within two months post-diagnosis), and 3) other coverage patterns. Difference-in-differences (DD) models compared post- vs. pre-expansion changes in coverage patterns and 2-year overall survival in 11 SEER expansion states vs. four non-expansion states, adjusting for sociodemographic factors. Survival models additionally adjusted for coverage patterns to assess the extent to which the patterns accounted for expansion-associated survival changes. Results: The percentage with continuous Medicaid increased more in expansion states (52.9% to 67.5%) than non-expansion states (41.5% to 50.8%), leading to a net increase of 8.2 percentage points (ppts; 95% CI = 2.3 to 14.2; p = 0.007) in adjusted DD model. The percentage with newly gained Medicaid decreased more in expansion states (24.6% to 14.2%) than non-expansion states (31.8% to 24.5%), resulting in a net reduction of 7.9 ppts (95% CI = -13.9 to -1.9; p = 0.010). No significant changes were observed post-expansion for other coverage patterns. Two-year overall survival increased in expansion states (85.7% to 86.9%) but declined in non-expansion states (87.7% to 82.9%), yielding a net increase of 6.2 ppt (95% CI = 2.8 to 9.6; p < 0.001) in adjusted DD model. This association was slightly attenuated after further adjusting for coverage patterns (DD = 5.9 ppts; 95% CI = 2.5 to 9.3; p < 0.001), suggesting coverage continuity accounted for approximately 4.9% of the expansion-associated gain in 2-year survival. Conclusions: Medicaid expansion was associated with improved coverage continuity pre-/peri-diagnosis and better early survival among Medicaid-insured children with leukemia or lymphoma. Amid ongoing Medicaid policy changes, these findings add evidence that stable coverage matters for vulnerable children. Future work will evaluate longer-term outcomes (e.g., 5-year survival).