Treatment with enzalutamide (Xtandi) or abiraterone (Zytiga) led to a median overall survival of 30 months for African-American men as compared with 26 months for white patients. The difference proved to be statistically significant in both univariate (P=0.0435) and multivariate (P=0.0020) analyses.
The results are consistent with and build on previous data suggesting that African-American men with mCRPC can achieve outcomes as good as or better than those of their white counterparts, Megan McNamara, MD, of Duke University in Durham, North Carolina, reported during a press briefing prior to the Genitourinary Cancers Symposium, which begins Thursday.
"I think these findings really reinforce what is already the standard of care. These are standard-of-care treatments, and it's important that we have real-world studies to show that standard-of-care treatments work. They don't necessarily change what we're doing but they reinforce what we're already doing. It's important that we make sure that every African-American man is eligible for these medications gets them."
"The specific new finding is that we're showing a survival benefit with androgen-directed therapy," she added.
The data are provocative and add to an emerging database with the potential to "change the way we think about racial differences," if confirmed in prospective studies, said press briefing moderator Robert Dreicer, MD, a clinical and scientific expert for the American Society of Clinical Oncology.
"These findings provide important evidence that African-American men with metastatic prostate cancer, who have long had among the highest incidence and poorest outcomes of this disease, may now have better survival when treated with newer prostate cancer medications, as compared with other men," said Dreicer, of the University of Virginia in Charlottesville.
A large volume of evidence has demonstrated that African-American men have an increased risk of developing mCRPC and have worse survival as compared with Caucasians. Recently, several studies suggested that African-Americans with mCRPC can achieve better outcomes than do white patients with newer treatments for the disease, including docetaxel, sipuleucel-T (Provenge), and abiraterone.
To date, limited data have emerged regarding survival of African-American and Caucasian men who received abiraterone or enzalutamide for mCRPC and no prior exposure to chemotherapy. To address the issue, McNamara and colleagues searched the Veterans Health Administration database to identify patients treated for mCRPC from April 2013 through March 2018. Eligible patients had no evidence of treatment with chemotherapy within the previous 12 months and had at least one prescription for abiraterone or enzalutamide.
The data analysis included 2,910 patients: 787 African Americans and 2,123 Caucasians. The African-American men were older (74 vs 71) and had more comorbidities, including hypertension (77.1% vs 67.1%, P<0.0001), type 2 diabetes (38.1% vs 29.3%, P<0.0001) and liver abnormalities or overt damage (8.8% vs 5.2%, P=0.0003).
Overall survival, defined as the time from first prescription claim for abiraterone or enzalutamide to date of death, was the primary outcome. The 4-month difference favoring African-American men translated into a hazard ratio of 0.887 in a univariate analysis (95% CI 0.790-0.996). A multivariate analysis that adjusted for age and comorbidities yielded a hazard ratio of 0.826 (95% CI 0.732-0.933).
"When controlling for access to care -- through a single-payer system -- in chemotherapy-naive metastatic castration-resistant prostate cancer patients, African Americans may have better overall survival than Caucasians treated with abiraterone acetate or enzalutamide," McNamara said in conclusion. "These retrospective data emphasize the need for prospective trials to validate these findings and investigate the mechanism underlying racial disparities in survival outcomes of metastatic castration-resistant prostate cancer patients treated with new hormonal therapies."
The Genitourinary Cancers Symposium begins here Thursday and continues through Saturday. The symposium is cosponsored by ASCO, the American Society for Radiation Oncology, and the Society of Urologic Oncology.