African-Americans with metastatic castration-resistant prostate cancer live longer after treatment with the androgen inhibitors Zytiga (abiraterone acetate) or Xtandi (enzalutamide) than white men, a new study reports.
Historically, African-Americans diagnosed with prostate cancer have had worse survival outcomes than whites. The reasons for this are complex and likely involve a number of interconnected factors, from socioeconomic inequalities to genetic differences.
Yet, a new study suggests this disparity isn’t present when comparing African-American and white men treated with Zytiga (by Janssen Oncology), or Xtandi (by Pfizer and Astellas). In fact, the opposite may be true. Both of these medicines target the production of androgens, which are hormones that often help drive prostate cancer growth.
The research was presented at the 2019 Genitourinary Cancers Symposium, a meeting of the American Society of Clinical Oncology (ASCO), under the title, “Overall survival by race in chemotherapy-naïve metastatic castration-resistant prostate cancer (mCRPC) patients treated with abiraterone acetate or enzalutamide.”
The study retrospectively analyzed nearly 3,000 patients — about two-thirds of whom were white and one-third African American — with metastatic castration-resistant prostate cancer who had not received any prior chemotherapy for their condition.
Patients were treated for prostate cancer with either Zytiga or Xtandi from April 2013 to March 2018, and followed up with for an average of a year-and-a-half. The data from these patients was retrieved from the U.S. Veterans Health Administration database, and treatment outcomes were compared.
There were some differences between both racial groups: African-Americans were more likely to have high blood pressure, type 2 diabetes, and liver problems.
The average overall survival for African-Americans was 30 months, whereas the average overall survival for whites was only 26 months. This represented a 12% higher chance of survival among African-Americans than for whites, which increased even further (to 17%) even when other factors, such as age and other health issues, were taken into account.
“We don’t really know why this is occurring, but it is definitely something that demands further research,” Megan Ann McNamara, one of the researchers, said in a press release.
Conceivably, this difference in treatment outcome could be genetic — for example, variants in androgen-related genes that are more common in African-American men that make their tumors more likely to respond to treatments that target this pathway. But significant research will need to be done to confirm this association and to determine what its cause might be.