Background: While minoritized populations are less likely to participate in cancer trials, it is unknown whether social determinants of health (SDOH) explain these inequities. Here we identify SDOH factors that contribute to racial/ethnic inequities in clinical trial participation among patients with 22 common cancers.
Methods: This retrospective cohort study used electronic health record data (2011-2023) linked to neighborhood (Census tract) data from multiple sources. Patients were followed from diagnosis to clinical study drug receipt (proxy for trial participation), death, or last recorded activity. Associations were assessed using Cox proportional hazards models adjusted for clinical factors (diagnosis year, age, sex, performance status, stage, cancer type). To elucidate which area-level SDOH underlie racial/ethnic inequities, mediation analysis was performed using nonlinear multiple additive regression tree models.
Results: This study included 250105 patients (64.7% non-Latinx White, 8.9% non-Latinx Black, 5.2% Latinx). Black and Latinx patients were more likely to live in economically/socially marginalized areas (eg, disproportionately minoritized [measure of segregation], limited English proficiency [LEP], low vehicle ownership) than White patients. Black (3.7%; HR = 0.55 [CI = 0.52-0.60]) and Latinx patients (4.4%; HR = 0.63 [CI = 0.58-0.69]) were less likely to participate in trials than White patients (6.3%). Fewer patients in economically/socially marginalized neighborhoods participated in trials. Mediators explained 62.2% (CI = 49.5%-74.8%) of participation inequities between Black and White patients; area-level SDOH-including segregation (29.9% [CI = 21.2%-38.6%]) and vehicle ownership (11.6% [CI = 7.0%-16.1%])-were the most important mediators. Similarly, Latinx-White participation inequities were mediated (65.1%, [CI = 49.8%-80.3%]) by area-level SDOH such as segregation (39.8% [CI = 28.3%-51.3%]), LEP (11.6%, [CI = 2.8%-20.4%]), and vehicle ownership (9.6% [CI = 5.8%-13.5%]).
Conclusions: To improve racial/ethnic diversity in cancer trials, efforts to address barriers related to adverse neighborhood SDOH factors are necessary.