Using data from 11,464 Indiana residents under age 65 with primary lung cancer, this study assessed the impact of Medicaid expansion on stage at diagnosis and rates of foregoing cancer-directed surgery (CDS). Geospatial hotspot analysis revealed substantial heterogeneity: areas of late-stage diagnosis increased by 687 km² (184%) after expansion, with hotspot rates remaining markedly higher than non-hotspots. Difference-in-differences regression showed a 7-percentage-point decrease in late-stage presentation among Medicaid/self-pay patients post-expansion, but no meaningful reduction in rates of foregoing CDS. Medicaid/self-pay patients continued to forgo surgery at significantly higher rates than privately insured individuals, suggesting that insurance expansion alone is insufficient to overcome structural barriers to surgical cancer care. These findings highlight the need for tailored interventions addressing local disparities, healthcare access, and social determinants that influence treatment uptake beyond insurance coverage alone.