Medicaid Expansion and Place-Based Disparities in Non–Small Cell Lung Cancer Diagnosis and Survival

Importance: Non-small cell lung cancer (NSCLC) is the leading cause of cancer death in the US, with substantial socioeconomic, racial, and geographic disparities. Objective: To evaluate the association between Medicaid expansion and place-based disparities in insurance coverage, early-stage diagnosis, and 3-year overall survival among patients diagnosed with NSCLC. Design, Setting, and Participants: This cohort study used difference-in-differences (DD) and difference-in-differences-in-differences (DDD) analyses in the population-based Cancer Incidence in North America of the North American Association of Central Cancer Registries database. For analyses of insurance coverage and early-stage diagnosis, participants included patients aged 18 to 64 years with NSCLC newly diagnosed from January 1, 2009, to December 31, 2013 (defined as the pre-expansion period), and from January 1, 2015, to December 31, 2019 (defined as the postexpansion period), from 26 states and Washington, DC, that expanded Medicaid eligibility by 2014 and 17 nonexpansion states as of 2019. Survival analysis included patients aged 18 to 61 years in January 1, 2009, to December 31, 2012 (defined as the pre-expansion period), and January 1, 2015, to December 31, 2018 (defined as the postexpansion period), from 26 expansion states and 16 nonexpansion states. For both analyses, 2014 was excluded as the washout period. Data were analyzed from August 1, 2023, to April 30, 2026. Exposure: Medicaid expansion. Main Outcomes and Measures: Outcomes included insurance coverage, localized-stage diagnosis, and 3-year overall survival. Linear probability regressions and flexible parametric survival models were fitted, adjusting for age, sex, and county-level metropolitan status and social deprivation. Stratified analyses were conducted within subgroups defined by census tract-level poverty and county-level poverty, metropolitan status, medically underserved areas, racialized economic residential segregation, and social deprivation. Results: Among 303 503 patients (164 901 [54.3%] male; 216 591 [71.4%] aged 55-64 years), health insurance coverage increased by 5.06 percentage points (pp) (95% CI, 4.80-5.32 pp) in expansion states and by 2.87 pp (95% CI, 2.59-3.16 pp) in nonexpansion states, resulting in adjusted DD of 2.22 pp (95% CI, 1.83-2.60 pp). Similarly, Medicaid expansion was associated with significant increases in localized-stage diagnosis (1.76 pp [95% CI, 1.21-2.30 pp]) and 3-year overall survival (1.89 pp [95% CI, 1.04-2.74 pp]). Improvements were greater among patients residing in socioeconomically disadvantaged areas. For example, the 3-year survival difference associated with Medicaid expansion was 4.22 pp (95% CI, 2.39-6.05 pp) in nonmetropolitan counties but 1.21 pp (95% CI, 0.26-2.17 pp) in metropolitan counties (P = .01 from DDD analysis). Conclusions and Relevance: In this nationwide cohort of patients with NSCLC, Medicaid expansion was associated with improved outcomes, especially among patients residing in socioeconomically vulnerable areas. Patterns are consistent with a narrowing of place-based disparities and support potential benefits of Medicaid expansion and possible implications of projected coverage losses.