Longer Survival in Black Men on Newer Prostate Cancer Drugs

Population-based studies have suggested that, compared with white men, black men are at higher risk of dying from prostate cancer. However, recent findings show that that isn't necessarily the case.

In the latest study, survival was longer for African American patients who were treated with the newer hormonal therapies. The findings come from an analysis of chemotherapy-naive patients with metastatic castration-resistant prostate cancer (mCRPC) who were treated with either abiraterone acetate (multiple brands) or enzalutamide (Xtandi, Astellas).

When controlling for access to care, which in this study was through a single-payer system, black patients lived 20% longer than white patients who received the same therapy.

The median overall survival was 30 months vs 26 months, favoring black patients.

"These results are consistent with prior results from clinical studies in metastatic castration-resistant prostate cancer populations involving docetaxel [multiple brands], sipuleucel-T [Provenge, Dendreon], and abiraterone," explained lead author Megan McNamara, MD, an assistant professor of medicine at Duke University School of Medicine, Durham, North Carolina.

McNamara presented the findings during a presscast that preceded the Genitourinary Cancers Symposium (GUCS) 2019.

"We know that African American men have higher risk of metastatic castration-resistant prostate cancer and worse survival than white men," she said. "However, despite this, there is also evidence to suggest that African American men with advanced prostate cancer may have better outcomes in response to several prostate cancer treatments.

"We don't really know why this is occurring, but it is definitely something that demands further research," McNamara said in a statement.

She said there is a need for prospective trials to validate these findings and to "investigate the mechanism underlying racial disparities in survival outcomes of mCRPC patients treated with new hormonal therapies."

Commenting on the study, Robert Dreicer, MD, MACP, FASCO, a clinical and scientific expert for the American Society of Clinical Oncology, who moderated the presscast, noted that "these data are very provocative, and it adds to an emerging database that has confirmed prospectively and has changed the way we think about racial differences."

Overall Survival Superior

For their study, McNamara and colleagues conducted a retrospective analysis using the Veterans Health Administration database for the period April 1, 2013, to March 31, 2018, to identify chemotherapy-naive patients with mCRPC who had received at least one prescription for abiraterone or enzalutamide.

Their analysis included 2910 patients, of whom 787 were black and 2123 were white. Black patients tended to be older (74 vs 71 years) and to have more comorbidities, including hypertension (77.1% vs 67.1%; P < .0001), type 2 diabetes (38.1% vs 29.3%; P < .0001), and liver damage or abnormality (8.8% vs 5.2%; P = .0003), as compared with white patients in the cohort.

Overall survival was defined as the interval from the first prescription claim for abiraterone or enzalutamide following castration to the date of death. The median follow‐up time was 570 days for black men and 561 days for whites.

In the unadjusted analysis, the median estimated overall survival was 910 days for blacks and 784 days for whites. Overall survival was superior for black patients (hazard ratio [HR] = 0.887). In the adjusted analysis, the benefit remained for black men: 918 days vs 781 days (HR = 0.826).

The study was funded by Pfizer. McNamara has received travel or accommodations expenses from Clovis Oncology; honoraria from Bayer and Exelixis; and research funding (institutional) from Bayer, Seattle Genetics/Astellas, Agensys, Clovis Oncology, and Janssen. Several coauthors have disclosed relationships with industry, as noted in the abstract.

Genitourinary Cancers Symposium (GUCS) 2019: Abstract 212. Presented February 14, 2019.

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