The effect of Medicaid expansion on time to treatment and survival in metastatic colorectal cancer: A statewide analysis.

Abstract

48 Background: Medicaid expansion (ME) has been associated with improvements in colorectal cancer outcomes, largely driven by stage migration from enhanced screening and earlier diagnosis. Whether ME affected clinical outcomes among patients with advanced disease remains poorly understood. Methods: We used a quasi-experimental, difference-in-differences design to assess the impact of ME on time to treatment (TTT) and overall survival (OS) among patients with metastatic (stage IV) colorectal cancer (CRC). We identified patients with stage IV CRC in the California Cancer Registry and fit Cox proportional hazards models with interaction terms comparing Medicaid versus privately insured patients across the pre- (2009–2013) and post-ME (2015–2019) periods, adjusting for individual-level clinical factors and geographic region. Results: We identified 8,199 patients with metastatic CRC diagnosed between 2009 and 2019. We found no significant difference in either TTT or OS for Medicaid patients relative to privately insured patients in the post ME vs pre ME period (Table). We did, however, find significant heterogeneity by geographic region with Medicaid patients in urban areas generally having smaller improvements in OS than patients living in rural areas. Conclusions: In this large, statewide cohort of patients with metastatic CRC, we found no evidence that ME improved timeliness of care or OS. More modest gains in OS among Medicaid patients in major metropolitan areas suggest that the benefits of expanded insurance coverage may be constrained by persistent barriers to delivering complex cancer care, such as administrative delays, inadequate provider networks, and limited system capacity. Difference-in-differences estimates for time to treatment and overall survival by insurance and region. Analysis DD estimator (95% CI) p-value Time-to-Treatment(Medicaid vs. Private) 0.97 (0.88-1.07) 0.59 Time-to-Treatment(SF Bay Area vs. Rural) 0.96 (0.74-1.25) 0.79 Overall Survival(Medicaid vs. Private) 0.99 (0.92-1.06) 0.67 Overall Survival(SF Bay Area vs. Rural) 1.27 (1.09-1.48) <0.01 CI, confidence interval; DD, difference-in-differences; SF, San Francisco. Time-to-treatment measures days between diagnosis and first dose of chemotherapy. DD estimator >1 signifies shorter time. Overall survival measures days between diagnosis and death from any cause. DD estimator > 1 signifies higher hazard of death.