Participant Diversity by Race, Ethnicity, and Sex in Rare Disease Clinical Trials: A Case Study of Eight Rare Cancers

• Rare cancer clinical trials appear to enroll less diverse participants than clinical trials more broadly and therefore may require additional considerations or unique solutions to diversify participant recruitment. These differences persisted within both NIH and non-NIH funded trials. The rare cancer clinical trials in this study were completed between 2004 and 2023.
• People from non-White, non-Hispanic racial and ethnic backgrounds tend to be underrepresented in the rare disease clinical trials we examined relative to the incidence rates for these groups.
• An increasing share of new oncology clinical trials are aimed at rare cancers or small subsets of more common cancers. Lack of diversity in these clinical trials will inhibit health equity for a growing number of patients, with underrepresented groups less likely to benefit from experimental treatments and health systems lacking information about the efficacy of treatments in diverse populations.
• Further federal engagement and coordination is needed to understand and overcome challenges to enrolling diverse populations in rare cancer clinical trials.

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