《患者保护和可负担医疗法案》（ACA）的医疗补充计划扩展导致全国范围内医疗补充计划的使用增加。然而，迄今为止尚未研究医疗补充计划扩展与临床试验的关联。本研究旨在探讨ACA医疗补充计划扩展的实施是否与医疗补充计划患者参与癌症临床试验的增加相关。本队列研究的数据来源是SWOG肿瘤研究网络的51,751名患者。包括1992年4月1日至2020年2月29日期间年龄在18至64岁之间并接受医疗补充计划或私人保险的治疗试验的所有患者。使用分段逻辑回归的中断时间序列分析。月度失业率和总统行政部门根据潜在的经济状况和国家行政政策调整以反映与医疗补充计划使用相关的差异。数据分析于2021年6月22日至2022年8月5日期间进行。ACA医疗补充计划扩展的实施时间为2014年1月1日，为自变量。分析了随时间变化的癌症临床试验中不同保险类型的患者数量和比例。总体而言，分析了51,751名患者的数据。平均年龄（标准差）为50.6（9.8）岁，67.3%的患者为女性，41.1%的患者年龄在50岁以下，9.1%使用医疗补充计划。在ACA医疗补充计划扩展后，患者使用医疗补充计划的比例年增长了19%（奥斯比比率[OR]为1.19；95%置信区间[CI]为1.11-1.28；P ＜.001），导致医疗补充计划患者数量比预期增加了52%（OR为1.52；95%CI为1.29-1.78；P ＜.001）。这种关联在于2014年至2015年采用医疗补充计划扩展的州中更为明显（OR为1.26；95%CI为1.15-1.38；P ＜.001），而在其他州中则较小（OR为1.08；95%CI为0.96-1.21；P = .20；P = .04表示相互作用）。到2020年2月，医疗补充计划患者的比例为17.8%（95%CI为15.0%-20.8%；P ＜.001），而如果没有ACA医疗补充计划扩展，预计比例为6.9%（95%CI为4.4%-10.3%；P ＜.001）。研究结果表明，ACA医疗补充计划扩展的实施与使用医疗补充计划的患者在癌症临床试验中的参与增加相关。对于寻求参与临床试验以及改善试验结果适用于各种背景的患者自信心的社会经济弱势患者来说，改善医疗补充计划参与临床试验的机会至关重要。

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.To examine whether the implementation of ACA Medicaid expansion was associated with increased participation of patients with Medicaid insurance in cancer clinical trials.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.Implementation of Medicaid expansion on January 1, 2014, was the independent exposure variable.The number and proportion of patients by insurance type enrolled in cancer clinical trials over time were analyzed.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).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.