Medicaid Expansion of the Patient Protection and Affordable Care Act and Participation of Patients With Medicaid in Cancer Clinical Trials

Importance: The Patient Protection and Affordable Care Act (ACA) Medicaid expansion resulted in increased use of Medicaid insurance nationwide. However, the association between Medicaid expansion and access to clinical trials has not been examined to date. Objective: To examine whether the implementation of ACA Medicaid expansion was associated with increased participation of patients with Medicaid insurance in cancer clinical trials. Design, Setting, and Participants: Data for this cohort study of 51 751 patients were from the SWOG Cancer Research Network. All patients aged 18 to 64 years and enrolled in treatment trials with Medicaid or private insurance between April 1, 1992, and February 29, 2020, were included. Interrupted time-series analysis with segmented logistic regression was used. The monthly unemployment rate and presidential administration were adjusted to reflect potential differences in Medicaid use associated with economic conditions and national administrative policies, respectively. Data analysis was conducted between June 22, 2021, and August 5, 2022. Exposure: Implementation of Medicaid expansion on January 1, 2014, was the independent exposure variable. Main Outcomes and Measures: The number and proportion of patients by insurance type enrolled in cancer clinical trials over time were analyzed. Results: Overall, data for 51 751 patients were analyzed. Mean (SD) age was 50.6 (9.8) years, 67.3% of patients were female, 41.1% were younger than 50 years, and 9.1% used Medicaid. A 19% annual increase (odds ratio OR, 1.19; 95% CI, 1.11-1.28; P < .001) was identified in the odds of patients using Medicaid after the ACA Medicaid expansion, resulting in a 52% increase (OR, 1.52; 95% CI, 1.29-1.78; P < .001) compared with what was expected in the number of Medicaid patients enrolled over time. The association was greater in states that adopted Medicaid expansion in 2014 to 2015 (OR, 1.26; 95% CI, 1.15-1.38; P < .001) compared with other states (OR, 1.08; 95% CI, 0.96-1.21; P = .20; P = .04 for interaction). By February 2020, the proportion of patients with Medicaid insurance was 17.8% (95% CI, 15.0%-20.8%; P < .001), whereas the expected proportion had ACA Medicaid expansion not occurred was 6.9% (95% CI, 4.4%-10.3%; P < .001). Conclusions and Relevance: Findings suggest that implementation of ACA Medicaid expansion was associated with increased participation of patients using Medicaid in cancer clinical trials. Improved participation in clinical trials for Medicaid-insured patients is critical for socioeconomically vulnerable patients seeking access to the newest treatments available in trials and for improving confidence that trial findings apply to patients of all backgrounds.