Conference Coverage

Survival of patients with mCRPC on hormone therapy differs by race



– When given the same hormonal therapy for chemotherapy-naive metastatic castration-resistant prostate cancer (mCRPC), African American men live about 4 months longer than do white men, finds a retrospective cohort study being reported at the 2019 Genitourinary Cancers Symposium.

“We know that African American men have a higher risk of mCRPC and worse survival than white men,” said lead study author Megan McNamara, MD, of Duke University, Durham, N.C. “However, despite this, there is also evidence to suggest that African Americans with advanced prostate cancer actually have better outcomes in response to several prostate cancer treatments compared to Caucasians.”

She and her colleagues analyzed data from the Veterans Health Administration database for a 5-year period (2013-2018), focusing on 2,123 white and 787 African American male veterans with chemotherapy-naive mCRPC who were treated with the anti-androgen abiraterone (Zytiga) or the androgen receptor inhibitor enzalutamide (Xtandi). Overall survival was measured from the first prescription claim for either drug following medical or surgical castration.

Main results reported in a presscast leading up to the symposium showed that with a median follow-up of about 1.6 years, median overall survival was 30 months for African American men, compared with 26 months for white men. The difference corresponded to a significantly lower risk of death for African American men in both univariate analysis (hazard ratio, 0.887; P = .0435) and multivariate analysis adjusted for age and comorbidities (HR, 0.826; P = .0020).

“When controlling for access to care through a single-payer system – in this case, the VA Health System – in chemotherapy-naive mCRPC patients, African Americans may have better overall survival than Caucasians when treated with abiraterone or enzalutamide,” Dr. McNamara summarized. “These results are consistent with what we have seen in prior studies in this population involving docetaxel (Taxotere), sipuleucel-T (Provenge), and abiraterone.”

Importantly, the data expand on previous findings for abiraterone in the Abi Race study, she noted. That study established that African American men had a better prostate-specific antigen (PSA) response to the drug (J Clin Oncol. 2018 Jun 7. doi: 10.1200/JCO.2018.36.18_suppl.LBA5009).

The new findings do not alter but rather reinforce current clinical practice, according to Dr. McNamara. “These are standard-of-care treatments, and it’s important that we have real-world studies that show that the standard-of-care treatments really work,” she elaborated. “So I don’t think that they necessarily change what we are doing. But they reinforce what we are already doing, and that it’s important that we make sure that every African American who is eligible for these medicines gets them.

“Our study is retrospective,” she acknowledged. “But it emphasizes the need for prospective trials in order to validate these findings and in order to try to understand the mechanism that underlies these differences in survival outcomes between African Americans and Caucasians with mCRPC when treated with these novel hormone therapies.”

The data are “very provocative, and it adds to an emerging database that if confirmed prospectively, really changes the way we think about racial differences,” said ASCO expert and presscast moderator Robert Dreicer, MD, MS, MACP, FASCO, deputy director and associate director of clinical research at the University of Virginia Cancer Center and professor of medicine and urology at the University of Virginia, Charlottesville.

Full results of the study will be reported at the symposium, which is sponsored by the American Society of Clinical Oncology, ASTRO, and the Society of Urologic Oncology.

Dr. McNamara disclosed that she receives travel, accommodations, and/or expenses from Clovis Oncology; honoraria from Bayer and Exelixis; and research funding (institutional) from Bayer, Seattle Genetics/Astellas, Agensys, Clovis Oncology, and Janssen. The study was funded by Pfizer.

SOURCE: McNamara MA et al. Abstract 212.

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