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Hormone therapies for prostate cancer benefit black men more than white men
SAN FRANCISCO — Chemotherapy-naive black men with metastatic castration-resistant prostate cancer appeared to survive longer with abiraterone acetate or enzalutamide than their white counterparts, according to a study presented at Genitourinary Cancers Symposium.
“We know that prostate cancer is the most common malignancy among U.S. men and the second leading cause of cancer-related death. Both abiraterone and enzalutamide are androgen-directed therapies that improve overall survival in men with metastatic castration-resistant prostate cancer,” Megan Ann McNamara, MD, assistant professor of medicine at Duke University School of Medicine, said during a presscast. “We know that African-Americans have higher risks of metastatic castration-resistant prostate cancer and worse survival than white men. However, there’s also evidence to suggest that African-Americans with advanced prostate cancer have better outcomes in response to several prostate cancer treatments compared with Caucasians.”
Abiraterone acetate (Zytiga, Janssen) was approved in 2013 and enzalutamide (Xtandi, Pfizer) was approved in 2014 for use in chemotherapy-naive men with metastatic castration-resistant prostate cancer.
In the retrospective study, McNamara and colleagues reviewed Veterans Health Administration data from April 1, 2013, to March 31, 2018, on men aged 18 years and older with prostate cancer (white men, n = 2,123; mean age, 74 years; black men, n = 787, mean age, 71 years) who underwent medical or surgical castration.
The researchers designated the study’s index date as the first prescription claim date for abiraterone acetate or enzalutamide after castration. Patients received no chemotherapy for 12 months before the index date and remained enrolled in a VA health plan for at least 12 months before and after the index date. The researchers followed the men until death or disenrollment from the VHA database.
Median follow-up was 570 days for black men and 561 days for white men.
The researchers found that compared with white men, black men had a greater likelihood of comorbid hypertension (77.1% vs. 67.1%; P < .0001), type 2 diabetes (38.1% vs. 29.3%; P < .0001) and liver damage or defect (8.8% vs. 5.2%; P = .0003).
Unadjusted analysis revealed median estimated OS of 910 days for black men treated with abiraterone or enzalutamide vs. 784 days for white men who received the same treatment; with OS favoring black men (HR = 0.88; 95% CI, 0.79-0.99). The adjusted analysis confirmed this finding, showing median estimated OS of 918 days for black men vs. 781 days for white men (HR = 0.82; 95% CI, 0.73-0.93).
The researchers — who also conducted the prospective Abi Race trial comparing outcomes among black and white men treated for prostate cancer with abiraterone acetate — plan to further investigate blood samples from that trial to understand any potential biological mechanisms that may drive racial differences in prostate cancer prevalence and treatment response.
“When controlling for access to care through a single-payer system, in this case the VA health system, in chemotherapy naive metastatic castration-resistant [patients with] prostate cancer, African-Americans may have better overall survival than Caucasians when treated with abiraterone or enzalutamide,” McNamara said. “Our study is retrospective, 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 metastatic, castration-resistant prostate cancer when treated with these novel hormone therapies.”– by Jennifer Byrne
Reference:
McNamara M, et al. Abstract 212. Presented at: Genitourinary Cancers Symposium; Feb. 14-16, 2019; San Francisco.
Disclosures: McNamara reports travel, accommodations and expenses from Clovis Oncology; honoraria from Bayer and Exelixis; and institutional research funding from Agensys, Bayer, Clovis Oncology, Janssen and Seattle Genetics/Astellas. Please see the abstract for all other authors’ relevant financial disclosures.