Mediators of racial/ethnic inequities in clinical trial participation among US patients with cancer, 2011-2022.

Abstract

6511 Background: In 2024, the US Food & Drug Administration will require drug sponsors to implement plans to improve racial/ethnic diversity in clinical trials. 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 identified SDOH factors that contribute to racial/ethnic inequities in clinical trial participation among patients with 22 solid and blood cancers. Methods: This retrospective study used the nationwide Flatiron Health electronic health record-derived de-identified database of adult patients with cancer (2011-2022). Area-level SDOH ( e.g., predominant race/ethnicity [proxy for segregation]) contextualizing where patients live were defined using the American Community Survey tract data. Patients were followed from cancer-specific diagnosis to clinical study drug receipt (proxy for trial participation), death, or last recorded activity. Associations of race/ethnicity and SDOH factors on trial participation were assessed using Cox proportional hazards models adjusted for clinical factors (diagnosis year, age, sex, performance status, stage, and cancer type). To elucidate which SDOH explain racial/ethnic inequities, mediation analysis was performed using nonlinear multiple additive regression trees models. Results: This study included 233,556 patients (median age: 68 years, 50.0% women; 65.6% non-Latinx [NL] White, 8.5% NL Black, 5.0% Latinx). Black and Latinx patients were more likely to live in marginalized areas ( i.e., disproportionately minoritized, low socioeconomic status, limited English proficiency, and low vehicle ownership) than White patients. Overall, 4.9% of patients participated in trials. Fewer patients from community practices or in marginalized neighborhoods participated in trials. Black (3.4%; hazard ratio [HR] 0.55, 95% confidence interval [CI]: 0.51- 0.60) and Latinx patients (3.6%; HR 0.57, CI: 0.52-0.63) were less likely to participate in trials than White patients (5.8%). Black-White trial inequities were substantially mediated (58%, CI: 47%-68%) by practice type ( e.g., community vs. academic center, 13%, CI: 10%-15%) and area-level SDOH ( e.g., segregation [33%, CI: 25%-44%] and vehicle ownership [12%, CI: 8%-15%]). Mediators explained 55% (CI: 38%-71%) of the Latinx-White trial participation inequity; area-level SDOH—including segregation (29%, CI: 13%-37%), limited English proficiency (15%, CI: 9%-25%), and vehicle ownership (8%, CI: 5%-12%)—were the most important mediators. Conclusions: SDOH factors, especially manifestations of structural racism such as segregation, explained a substantial proportion of racial/ethnic inequities in trial participation among patients with cancer. These findings can inform targeted efforts to increase racial/ethnic diversity in cancer trials.