African-Americans fare better with mCRPC treatments vs. Caucasians

May 7, 2019

African-American men with metastatic castration-resistant prostate cancer who were treated with abiraterone acetate (ZYTIGA) or enzalutamide (XTANDI) and who had not received prior chemotherapy lived 20% longer over 5 years compared with their Caucasian counterparts.

San Francisco-African-American men with metastatic castration-resistant prostate cancer (mCRPC) who were treated with abiraterone acetate (ZYTIGA) or enzalutamide (XTANDI) and who had not received prior chemotherapy lived 20% longer over 5 years compared with their Caucasian counterparts.

The finding, from a large retrospective clinical trial called Abi Race, was presented by Megan McNamara, MD, at the Genitourinary Cancers Symposium in San Francisco.

The study builds on a growing body of work in prostate cancer showing improved overall survival (OS) in African-Americans with mCRPC with various treatments compared with Caucasian men, said Dr. McNamara, of Duke University School of Medicine, Durham, NC.

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For example, an analysis of pooled data from nine randomized phase III clinical trials of men with mCRPC found better overall survival with African-Americans treated with docetaxel (Taxotere) compared with Caucasians after adjusting for established prognostic factors. African-American patients also had longer OS compared with Caucasians when treated with sipuleucel-T (Provenge) in an exploratory analysis of phase III trials, a finding that was confirmed in the PROCEED registry.

“In our Abi Race study, which was a small prospective study of 50 African-Americans and 50 white patients with mCRPC treated with abiraterone, there was an indication that the African-Americans had better prostate-specific antigen response,” Dr. McNamara told Urology Times.

Next:"We need to make sure that all African-Americans who are eligible for treatment with abiraterone or enzalutamide receive them.”“Even though we know that African-Americans have more aggressive prostate cancer and worse survival from prostate cancer, these treatments work in African-Americans, and they may even work better in African-Americans than they do in Caucasians. The message is that we need to make sure that all African-Americans who are eligible for treatment with abiraterone or enzalutamide receive them," she added.

She and colleagues identified 2,123 Caucasian and 787 African-American men with mCRPC who were at least 18 years of age and whose only prior treatment was surgical or medical castration from the Veterans Health Administration (VHA) database (April 1, 2013 to March 31, 2018). Among men with disease progression, only those who had been treated with either abiraterone acetate or enzalutamide were included. Outcomes were monitored until they either disenrolled from the VHA or died.

Mean ages were 74 years for Caucasian patients and 71 years for African-Americans. Compared with Caucasians, African-Americans had higher rates of hypertension (67.1% vs. 77.1%; p<.0001), type 2 diabetes (29.4% vs. 38.1%; p<.0001), and liver damage or abnormality (5.2% vs. 8.8%; p=.0003) but were less likely to have hyperlipidemia (54.7% vs. 48.3%; p=.002).

Median follow-up was 19 months for Caucasians and African-Americans. Median adjusted OS was 30 months in the African-American men compared with 26 months in the Caucasian men. Time to death was significantly better in the African-American men (adjusted HR: 0.826; p=.002).

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“We need to do prospective studies to validate these findings and to be able to collect correlatives so that we can understand the reason for this enhancement in survival,” said Dr. McNamara.

“Mining historic records in large databases can often help researchers home in on the patients who are more likely to benefit from certain medications,” said Robert Dreicer, MD, of the University of Virginia Cancer Center, Charlottesville, who moderated an American Society of Clinical Oncology press briefing.

“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,” added Dr. Dreicer, who was not involved with the study.

The study was sponsored by Pfizer. Dr. McNamara has received honoraria from Bayer and Exelixis; travel, accomodations, and expenses from Clovis Oncology; and institutional research funding from Agensys, Bayer, Clovis Oncology, Janssen, and Seattle Genetics/Astellas. For full disclosures, click here.