Black men with metastatic castration-resistant prostate cancer (CRPC) who received hormonal therapy with the adrenal inhibitor abiraterone had greater and longer-lasting responses compared with white men, according to the results of a late-breaking study (abstract LBA5009) presented at the 2018 American Society of Clinical Oncology (ASCO) Annual Meeting, held in Chicago June 1–5.
The prospective study found that black men were more likely to have a decline in prostate-specific antigen (PSA) and had a longer median time to PSA worsening than white men. The findings were presented by Daniel George, MD, professor of medicine and surgery at Duke University.
According to George, there is a higher risk of death from prostate cancer associated with black race than white race. Although reasons for this disparity are multifactorial, some of the difference is believed to be genetic. However, most clinical trials have included a disproportionately low percentage of minority participants. As a result, there is insufficient evidence about possible differences in treatment efficacy and side effects by race.
With this study, George and colleagues hypothesized that black men with advanced prostate cancer would respond better to abiraterone than white men. The Abi Race study included 50 black men and 50 white men with metastatic CRPC. All patients on the study received abiraterone at a dosage of 1,000 mg per day and prednisone at 10 mg per day, until disease progression or unacceptable toxicity.
The median radiographic progression-free survival was similar in black men and white men, at about 16.8 months. However, PSA progression–free survival varied, the researchers noted. The median PSA progression–free survival for black patients was 16.6 months, compared with 11.5 months for white patients.
In addition, black patients had numerically higher rates of PSA decline greater than or equal to 30% (82% vs 78%), 50% (74% vs 66%), or 80% (48% vs 38%), compared with white men. More white patients than black patients had no PSA decline.
Toxicity was also different between the arms. Black patients experienced higher rates of several hormonal-based toxicities, such as hyperglycemia, hypokalemia, and hot flashes, “suggesting perhaps a greater exposure risk to this medicine,” George said.
These results show that “race studies are possible,” George said.
“We absolutely need to do this because there are differences in outcomes of treatment and side effects that could have significant implications on how and when we use these drugs,” he said.
Commenting on the results, ASCO Expert Robert Dreicer, MD, said, “Racial and ethnic minorities continue to be underrepresented in clinical trials. This study should serve as a call for the entire cancer research community to make trials much more inclusive. When it comes to cancer treatments, people are not all alike, and it’s important to understand how different groups respond to different therapies.”