An analysis of 59 prostate cancer clinical trials based in North America and Europe found that the vast majority of enrollees were non-Hispanic white men, according to a study published by Rencsok et al in Cancer Epidemiology, Biomarkers & Prevention.

The proportion of white participants in prostate cancer clinical trials has largely remained above 80% since 1990, while the proportion of black or African American men in these trials decreased from 11.3% in 1995 to 2.8% in 2014.

“In the United States, less than 60% of prostate cancer cases occur in non-Hispanic white men, and roughly 22% of cases occur in non-Hispanic black men,” said Emily Rencsok, an MD/PhD student at the Harvard T.H. Chan School of Public Health and lead author of the study, in a statement. “However, when we analyzed the diversity of enrollment in nearly 60 prostate cancer clinical trials, we found that over 96% of participants were white.”

“It’s important to acknowledge the extent of underrepresentation of minority men in prostate cancer clinical trials so that we can find better ways to support their enrollment in future trials,” added Ms. Rencsok. “Black men have a disproportionate burden of prostate cancer incidence and mortality compared with white men, and the increased enrollment of black men in prostate cancer clinical trials will help us to learn more about these racial disparities, which could ultimately lead to improved treatment options for this patient population.” 

While previous analyses have shown that black men are underrepresented in prostate cancer clinical trials, these studies were often focused on a specific type of prostate cancer and were therefore limited to a small number of clinical trials, explained Ms. Rencsok. “By analyzing a larger number of prostate cancer clinical trials, we were able to conduct a comprehensive review of enrollment. Further, we could evaluate if the diversity of enrollment in these clinical trials has changed over time,” she said.

Methods

The multi-institutional researchers analyzed 72 global phase III and IV clinical trials analyzing prevention, screening, and treatment for patients with prostate cancer with enrollment start dates between 1987 and 2016. Of these 72 trials, 59 had available racial data, comprising approximately 844,000 participants.

Roughly 20% of these trials were publicly funded, whereas the remaining 80% were funded by pharmaceutical or biotechnology companies. Four screening trials were conducted in Canada or Europe, and the remaining 55 trials were conducted globally with primary centers in the United States.

Results

Of the 59 trials analyzed, 51 were treatment trials, 4 were prevention trials, and 4 were screening trials. The researchers found that the majority of participants in each of these three categories were non-Hispanic white men, comprising 83.4%, 84.6%, and 97.5% of the participants in the treatment, prevention, and screening trials, respectively. The black or African American category had the second-highest enrollment, comprising 6.7%, 8.5%, and 0.5% of the participants in the treatment, prevention, and screening trials, respectively. Overall, more than 96% of the participants enrolled in these prostate cancer clinical trials were non-Hispanic white men.

When the researchers analyzed the diversity of enrollment over time, they found that the proportion of black or African American men enrolled in prostate cancer clinical trials decreased from 11.3% in 1995 to 2.8% in 2014. Further, the researchers found that the proportion of white participants in these clinical trials has largely remained above 80% since 1990.

“In recent decades, we have continued to learn about the racial disparities in prostate cancer incidence and mortality, yet our trial enrollment is mostly [composed] of white men and does not reflect the populations that are most affected by this disease,” said Ms. Rencsok.

“We hope that this study broadly calls attention to the drastic underrepresentation of minority men in prostate cancer clinical trials, despite the increasing evidence of the racial disparities that exist in prostate cancer incidence and outcomes in these minority populations,” she added. “I think that we, as both a scientific and a clinical community, need to continue to dedicate intentional and specific resources toward the recruitment of underrepresented men into prostate cancer trials. Further, we should focus efforts into supporting the clinical trial infrastructure in the medical centers that predominantly serve underrepresented populations, both in the United States and globally.”

The researchers excluded nearly 200 clinical trials from their analyses due to a lack of available results, representing a limitation of this study. “It’s possible that the trials that we included are not generalizable to broad categories of phase III and IV prostate cancer clinical trials,” concluded Ms. Rencsok.

Disclosure: This study was supported by the Movember Foundation, the Prostate Cancer Foundation, and a training grant in cancer epidemiology, funded by the National Cancer Institute. For full disclosures of the study authors, visit cebp.aacrjournals.org.