Metastatic CRPC outcomes no worse for Black versus White men
medwireNews: Two studies reported at the ASCO Annual Meeting 2018 show that Black men with metastatic castration-resistant prostate cancer (CRPC) fare as well as White men, if not better, when treated with abiraterone or chemotherapy in the clinical trial setting.
“Black men are more than twice as likely to die of prostate cancer than white men 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,” Daniel George (Duke University, Durham, North Carolina, USA), lead author of the abiraterone study, told the press in Chicago, Illinois, USA.
For the Abi Race trial, George and colleagues recruited 100 patients with metastatic CRPC – 50 of whom self-identified as Black and 50 as White – and treated them with the standard regimen of abiraterone acetate 1000 mg/day and prednisone 5 mg twice a day until disease progression or unacceptable toxicity.
The primary endpoint of time to radiographic progression did not differ significantly between the Black and White participants (median 16.7 vs 16.5 months), but Black men had a longer time to prostate-specific antigen (PSA) progression, at a median of 16.6 months compared with 11.5 months for White men.
Moreover, a larger proportion of Black patients experienced PSA declines than their White counterparts. Specifically, a PSA decline of 30% or more was observed in 82% of Black men and 78% of White men, while the rates for a PSA reduction of more than 90% were 48% and 38%, respectively.
In order to understand the reasons for these differences in response, the study authors looked at genetics, finding differences between Black and White men in the single nucleotide polymorphism profiles of genes involved in androgen metabolism and transport. The researchers intend to conduct additional molecular analyses to gain further insight into factors underlying the differences in outcomes.
The second study was a meta-analysis of individual patient data from nine phase III randomized controlled trials investigating docetaxel plus prednisone-based regimens. Of the total 8871 participants, the 500 Black and 7528 White men were included in the analysis.
Median overall survival was similar for the groups, at 21.0 months for Black participants and 21.2 months for White participants.
But after accounting for prognostic factors such as age, performance status, and PSA level, Black men had a significant 19% reduced risk for death relative to White participants, reported lead author Susan Halabi, also from Duke University.
She speculated that the lower mortality risk in Black men “may reflect differences in the biology of the disease, or it may be that black men have better tolerability to [the] docetaxel-prednisone combination.”
Commenting on the findings, ASCO expert Robert Dreicer said that “[t]his research shows that by providing equal access to treatment, we can reduce racial disparities in outcomes for men with advanced prostate cancer,” adding that these results “should serve as a call for the entire cancer research community to make trials much more inclusive.”
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