Chicago, IL—In the United States, black men are twice as likely to die from prostate cancer as white men, and they are often diagnosed at a younger age and at later stages of the disease. The reasons for these discrepancies are unclear, but the resounding message from 2 new studies presented at ASCO 2018 is that when American black men have access to good care, their response to treatment and their survival rates are at least as good as, and possibly better than, those for American white men.
Taken together, these studies stress the need to increase participation in US clinical trials for black men with prostate cancer to give them access to high-quality treatments and improve their disease-specific survival.
Study I: Participation in Clinical Trials
In the first study, a pooled analysis of data from 9 phase 3 clinical trials with a total of 8828 men with metastatic castration-resistant prostate cancer (CRPC) showed that men who received chemotherapy had equivalent survival rates, regardless of their race.
The median survival rate was similar among black and white men—approximately 21 months in each cohort. In addition, an analysis adjusted for poor prognostic risk factors showed that black men had a 19% lower risk of death than white men if they participated in clinical trials.
Approximately 85% of the men enrolled in these trials were white, 6% were black, 5% were Asian, and 4% were "other or unknown race." For this analysis, only black men and white men were included, with a total of 8828 men. All men received docetaxel plus prednisone or a regimen containing these drugs plus other drugs.
"This study underscores the importance of increasing the participation of racial minorities in clinical trials. Every patient who participates in a clinical trial contributes to improving care, and all patients should have the opportunity to receive needed therapies," said lead investigator Susan Halabi, PhD, FASCO, Professor of Biostatistics and Bioinformatics, Duke University Medical Center, Durham, NC.
ASCO Expert Robert Dreicer, MD, MS, MACP, FASCO, Deputy Director, University of Virginia Cancer Center, Charlottesville, said, "I would argue that this tells us that black men [in the United States] can have better survival on conventional therapy. The study emphasizes access to care. When we treat black men, they do well."
Study II: Abiraterone Elicits Robust Responses in Black Men
In the second study of American men with metastatic CRPC who received abiraterone acetate (Zytiga) plus prednisone, responses were more robust among black men than in white men, according to the results of a prospective clinical trial of 100 patients.
Black men were more likely to have a decline in prostate-specific antigen (PSA), a surrogate for response, and had a 5-month longer time to PSA worsening compared with white men.
The investigators said this is the first prospective study to compare outcomes with abiraterone in black men and white men with advanced prostate cancer. These findings confirm previous observations suggesting that black men have a stronger response to abiraterone.
"Black men [in the United States] are more than twice as likely to die of prostate cancer and are generally thought to have worse prostate cancer outcomes. Our study suggests that when black men and white men with advanced prostate cancer are given the same hormone treatment, this is not the case," stated lead investigator Daniel J. George, MD, Director, Prostate & Urologic Cancer Program, Duke Cancer Institute, Durham, NC.
"Our research underscores the importance of specifically studying genetically diverse populations and raising awareness of these results, so that everyone who can benefit from abiraterone is offered this treatment."
The Abi Race clinical trial enrolled 100 men with metastatic CRPC, including 50 black men and 50 white men. All men received abiraterone acetate plus prednisone until disease progression or until they had unacceptable side effects.
Time to radiographic progression was similar between the 2 cohorts, but racial differences emerged related to PSA. The median PSA progression-free survival (PFS) was 16.8 months in black men and 11.5 months in white men.
After treatment with abiraterone, a greater percentage of black men than white men had PSA declines as follows:
- PSA ≥90%, 48% vs 39%, respectively
- PSA ≥50%, 75% vs 66%, respectively
- PSA ≥30%, 86% vs 76%, respectively.
Imaging scans revealed a similar median PFS for black men and white men—16.8 months. Side effects were similar between the 2 cohorts for the most part, but white men reported fatigue more often (40% vs 26%). In addition, twice as many black men as white men had a low potassium level requiring corrective treatment (36% vs 18%, respectively).
"The take-home message of this pilot study is that racial group studies are feasible, laying the groundwork for future studies. We need to understand the differences in treatment outcomes and side effects and genetic differences, because this can influence our choice of therapy," Dr George stated.
"We didn't need a clinical trial to give them [black men] standard of care. We need to educate physicians to treat blacks. Perhaps the problem is a health system approach. It is reassuring to us that patients can do well on standard therapy, and maybe they can do even better," Dr George added.