The increasing trend of the globalization of clinical trials is contributing to a widening disparity in the enrollment of Black patients with cancer, according to the results of a study published in Cancer.

“The enrollment of Black patients in cancer clinical trials continues to trend far below the true prevalence of disease in Black patients in the United States,” the authors reported. They added that “[a] potentially overlooked contributor to the underenrollment of Black patients may be the increasing enrollment of cancer trials in countries outside the United States.”

The study evaluated information about the race of patients enrolled and location of clinical trial accrual for all cancer drugs approved from 2015 to 2018 by the US Food & Drug Administration. Trials were assigned a disparity score, which was calculated based on the proportion of Black patients enrolled and the estimated burden of the cancer in the Black population.

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There were 35 drug approvals from 49 global clinical trials with available race data. Across these trials, 2.5% of patients were Black. The median disparity score was 0.19, with a score of 1 indicating no disparity between clinical trial enrollment and burden of disease.

There were 64% of patients enrolled outside the United States across 21 trials with accrual location data. Within these trials, 3.2% of patients enrolled were Black, and the median disparity score was 0.23.

A greater proportion of patients enrolled outside the United States was significantly associated with a worse disparity score (P =.007). Black patients comprised a median of 2% of all subjects in trials that enrolled less than 50% of patients from within the United States. The proportion of Black patients increased to a median of 5% in trials that enrolled 50% or more patients from within the United States (odds ratio, 2.1; 95% CI, 1.1-41). This also resulted in a difference in the disparity score, which was 0.19 and 0.47, respectively, for trials that accrued the majority of their patients outside or within the United States.

The authors concluded that “The impact of global trials on domestic clinical trial generalizability warrants further consideration from a regulatory and policy standpoint.”

Disclosures: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ affiliations.


Tharakan S, Zhong X, Galsky MD. The impact of the globalization of cancer clinical trials on the enrollment of black patients. Cancer. Published online March 8, 2021. doi: 10.1002/cncr.33463