CHICAGO—African-American men with metastatic castration-resistant prostate cancer had the same overall survival compared to Caucasian men, according to a retrospective analysis of nine phase III clinical trials (Abstract LBA5005). Study findings were presented at the 2018 ASCO Annual Meeting.
“Despite the overall declining trends in incidence and mortality rates, African-American men have higher incidence and mortality rate than white men. In addition they are diagnosed at a later stage for prostate cancer than Caucasian men [and] they have unequal access to health care,” said study author Susan Halabi, PhD, Professor of Biostatistics and Bioinformatics at Duke University.
Based on that information, the study authors hypothesized that African-American men with metastatic castration-resistant prostate cancer have worse survival outcomes than Caucasian men.
To test their hypothesis, the researchers retrospectively identified nine randomized, phase III clinical trials, of which six were industry sponsored and three were from the NCI National Clinical Trials Network.
From the trials, the researchers pooled 8,820 men with metastatic castration-resistant prostate cancer. Of those men, 7,528 were Caucasian (85%), 500 were African-American (6%), 424 were Asian (5%), and 368 were a different or unknown race (4%). Only Caucasian and African-American men were included in the analysis, totaling about 8,000 men.
Trial participants were all chemotherapy-naïve and received either docetaxel and prednisone or a regimen that included docetaxel and prednisone as treatment. The primary endpoint for all the trials was overall survival.
“This is the largest analysis comparing survival outcomes in African-American versus Caucasian men with advanced and lethal prostate cancer that are treated with docetaxel and prednisone,” said Halabi.
Study Findings & Implications
The retrospective analysis revealed that the median survival was 21 months for both African-American men and Caucasian men with metastatic castration-resistant prostate cancer.
By controlling for a variety of factors, including age, metastasis site, and prostate-specific antigen level, the researchers determined the hazard ratio to be 0.81 (P=0.004), which translates to a 19 percent lower relative risk of death for African-American men compared with Caucasian men.
When the analysis was restricted to the three trials conducted by the NCI National Clinical Trials Network, a median overall survival difference of 1 month was found (20 months for Caucasian men and 21 months for African-American men). The hazard ratio of 0.76 (P<0.0001) translates to a 24 percent lower relative risk of death for African-American men with advanced prostate cancer compared with Caucasian men.
Halabi described the 24 percent lower relative risk of death for African-American men in the three NCI National Clinical Trials Network as “even more striking” than the 19 percent lower relative risk for African-American men in all nine trials.
“Because black men have often been associated with more advanced disease or more aggressive disease at diagnosis, the thinking was that they will therefore have poorer outcomes,” said Neha Vapiwala, MD, Associate Professor of Radiation Oncology at the Hospital of the University of Pennsylvania, Philadelphia. “What is really incredible is that this [study] does appear to put a question mark on what has long been believed.”
Vapiwala also commented on the finding that suggests a lower risk of death for African-American men with metastatic castration-resistant prostate cancer. “I think that these are very provocative findings, but I don't think we can begin to understand or comment on why this would be, other than to say it's pretty shocking and kind of goes against how we generally view comorbidities and how we generally view disease.”
These findings were complemented by those from a prospective trial also presented at ASCO (Abstract LBA5009). The trial enrolled African-American men and Caucasian men with metastatic castration-resistant prostate cancer, and participants were treated with standard of care abiraterone acetate plus prednisone. The researchers found that both groups of men had similar radiographic progression-free survival, suggesting African-American men with advanced prostate cancer can have similar outcomes to Caucasian men.
The study researchers also found that trial enrollment varied by sponsor type. For industry trials, 96 percent of participants were Caucasian and 4 percent were African-American. In contrast, for the NCI National Clinical Trials Network, 88 percent of participants were Caucasian and 12 percent were African-American. A possible explanation for this, Halabi noted, is that “the NCI National Clinical Trials Network were conducted in the U.S., whereas industry-sponsored trials were conducted globally.”
Because the results were from phase III clinical trials, Halabi said they cannot be generalized to the U.S. population. However, others in the field disagreed, asserting a more optimistic view of the study implications.
“Despite my colleague's emphasis that this cannot be generalized to the U.S. population, I would argue that what this tells us is pretty striking, that African-American men have a potentially better survival by getting on conventional therapy,” said ASCO Expert Robert Dreicer, MD. He noted that this study shows that, when African-American men with advanced prostate cancer are treated, “they do well.”
Vapiwala echoed a similar sentiment, saying generalizability of clinical trial results is always a limitation. “What this does is at least raise some hope, certainly in my mind and hopefully for African-American men with prostate cancer or with strong family histories of prostate cancer.”
Senior Vice President and Chief Medical Officer of ASCO, Richard Schilsky, MD, also commented on the study, saying, “The bottom line is, in a sense, that African-American men with advanced prostate cancer need to get to an oncologist. Ideally, [they] need to get on a clinical trial, and if they do, their outcomes are every bit as good as Caucasian men, if not even a little bit better.”
Call to Action
Although not the purpose, the study does highlight the importance of enrolling minority groups in clinical trials. Vapiwala said that racial and ethnic minority enrollment in clinical trials tends to be “significantly” lower compared to Caucasians, and this limits what can be studied. “What Dr. Halabi and her team were able to do here is gain power in numbers by pooling patients from many different trials.”
Halabi stressed that new methodologies for enrolling a higher number of African-American men should be “actively” pursued and “rigorously” implemented so minority groups are well-represented on trials.
Christina Bennett is a contributing writer.