2019 GU Cancers Symposium: Study Evaluates Survival by Race in Metastatic Castration-Resistant Prostate Cancer
A large, retrospective study analyzing 5 years of data from the Veterans Health Administration (VHA) found that African American men with chemotherapy-naive, metastatic, castration-resistant prostate cancer who were treated with abiraterone acetate or enzalutamide lived 20% longer compared with white men who received the same treatment. These findings will be presented by McNamara et al at the upcoming 2019 Genitourinary Cancers Symposium in San Francisco, California (Abstract 212).
“We’ve historically seen that prostate cancer is more common, more aggressive, and more lethal in African American [men] compared with men of other racial groups,” said lead study author Megan McNamara, MD, Assistant Professor of Medicine at the Duke University School of Medicine. “Balancing against other health-related risks, we found that treatment with newer hormonal medicines led to a significantly greater survival for African American men in this analysis, compared with white men.”
About the Study
Researchers analyzed VHA data from April 2013 to March 2018, focusing on men with prostate cancer who were age 18 or older whose only prior treatment was surgical or medical castration. Among men with disease that had progressed, researchers included only those who had been treated with either abiraterone acetate or enzalutamide. These medications were approved in 2013 and 2014, respectively, for use in men with metastatic castration-resistant prostate cancer who had not received chemotherapy. Investigators monitored patients’ health outcomes until they either unenrolled from the VHA or died.
Altogether, the analysis included data from 2,123 white and 787 African American men with metastatic castration-resistant prostate cancer with mean ages of 74 and 71, respectively. Higher rates of hypertension, type II diabetes, and liver damage or abnormality were seen among African American men in the study as compared with white men in the study.
Key Findings
From the unadjusted analysis, the median Kaplan-Meier estimated overall survival (OS) was 910 days for African American men and 784 days for white men; African American men had better OS than white men (hazard ratio [HR] = 0.887; 95% confidence interval [CI] = 0.790–0.996). From the adjusted analysis, the median Kaplan-Meier estimated OS was 918 days for African American men and 781 days for white men; African American men still had better OS (HR = 0.826; 95% CI = 0.732–0.933).
Next Steps
This research group conducted a prospective clinical trial—called Abi Race—exploring prostate cancer outcomes in African American men and white men treated with abiraterone acetate. Initial findings from the Abi Race trial were presented by George et al at the 2018 ASCO Annual Meeting (Abstract 5009), demonstrating better PSA response among African American men with metastatic castration-resistant prostate cancer treated with abiraterone acetate compared with white men.
Additional analyses of blood samples from that trial are ongoing to investigate whether variations in key genes involved in androgen metabolism and transport may help explain some of the biology behind racial differences in treatment response. It is hoped that these results will lead to a better understanding of why African American men live longer than white men when treated with certain medicines for prostate cancer, and why African American men have a higher incidence of prostate cancer than white men.
“An important goal of the study is to understand why some men respond better to certain treatments for prostate cancer than others so that we can tailor treatments more effectively,” said Dr. McNamara. “Finding biomarkers that can guide development of targeted therapies is the ultimate goal.”
Commentary
“When it comes to cancer treatments, it’s important to understand how different groups respond to different therapies. Mining historic records in large databases can often help researchers home in on the patients who are more likely to benefit from certain medications. 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 ASCO Expert Robert Dreicer, MD, MS, MACP, FASCO.
Disclosure: This study was sponsored by Pfizer. The study authors' full disclosures can be found at coi.asco.org.
For more information about the 2019 GU Cancers Symposium News Planning Team, click here.
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
