Racial and Ethnic Minorities Are Severely Underrepresented in Cancer Clinical Trials

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Precision medicine incorporates multiple genetic, tumor-, and patient-specific factors to stratify patients into groups to help guide treatment decision-making. More widespread use of this approach has led to improved patient outcomes. However, these improvements have not been realized in real-world outcomes when patient race or ethnicity is included in further analysis. One possible reason is the underrepresentation of minority groups among clinical trial enrollees. Racial and ethnic differences occur in cancer types, and the lack of clinical trial diversity has resulted in the development of interventions that can have lower efficacy or higher toxicity in different populations.1 One example is the cancer chemotherapy drug 5-fluorouracil, which has higher toxicity rates in non-white/European populations.1 When this chemotherapy agent was undergoing clinical trials, white/European participants were overrepresented in the studies and the more severe adverse side effects in minority groups were missed.1 The same problem is also present in precision medicine clinical trials. Discoveries made in precision medicine may not be applicable across the general population, particularly if there is not equal representation in a trial patient population.

Aldrighetti and colleagues conducted a cross-sectional study that analyzed race and ethnicity reporting in breast, colorectal, lung, and prostate cancer studies in the United States to determine if these patient populations were representative of the overall cancer patient population in the United States. Under- and overrepresentation was presented as a ratio. Overrepresentation was indicated by ratios >1, while ratios <1 indicated underrepresentation. Patient demographics were obtained from the ClinicalTrials.gov website and collaborated by comparison to primary journal articles, abstracts, and/or presentations. Cancer incidence by race and ethnicity was gathered from the National Cancer Institute’s Surveillance, Epidemiology, and End Results Program database.

There were 93 studies evaluated with 5867 participants in these clinical trials. Non-Hispanic whites accounted for 82.3% of study participants, 10% of participants were black, and 4.1% of total participants were Asian. The ratio of Asian participants was 1.46, for non-Hispanic whites the ratio was 1.35, for black participants the ratio was 0.49, for American Indian and Alaska Native participants the ratio was 0.43, and for Hispanic study participants the ratio was 0.24. When individual cancer sites were analyzed, white participants were found to be overrepresented in all studies evaluated, and Hispanic and black participants were underrepresented in the studies.

There is a large underrepresentation of racial and ethnicity minority patients in breast, colorectal, lung, and prostate cancer precision medicine clinical trials.


Aldrighetti CM, Niemierko A, Van Allen E, et al. Racial and ethnic disparities among participants in precision oncology clinical studies. JAMA Netw Open. 2021;4:e2133205.


  1. Yates I, Byrne J, Donahue S, et al. Representation in clinical trials: a review on reaching underrepresented populations in research. Association of Clinical Research Professionals. August 10, 2020. https://acrpnet.org/2020/08/10/representation-in-clinical-trials-a-review-on-reaching-underrepresented-populations-in-research. Accessed December 1, 2021.

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