Rethinking race and prostate cancer outcomes

Dr. Gomella, a member of the Urology TimesEditorial Council, is chairman of the department of urology, Sidney Kimmel Cancer Center, Thomas Jefferson University, Philadelphia.

It is well established that African-American men are more likely to develop prostate cancer and experience higher mortality than other ethnic groups. Most research has focused on determining the causes of prostate cancer in this high-risk group. Numerous studies have evaluated socioeconomic issues, participation in screening, disparities in care for early disease, lifestyle issues, dietary factors, obesity, physical activity and others to identify potential causes.

However, these studies have often been conflicting and inconclusive. While genomics and other biologic analysis are a relatively new focus of these investigations, the complex interactions among all of these factors that may cause prostate cancer remain incompletely understood.

Two provocative studies reported at the 2018 ASCO annual meeting provide additional insight into prostate cancer racial disparities in a different group of patients, namely men with advanced prostate cancer who participated in a variety of clinical trials. In a large analysis of these trials by Halabi and associates, the relative risk of death was found to be 19% lower for African-American men than for Caucasian men.

In a clinical trial of 100 men balanced by race reported by George and associates using abiraterone acetate (ZYTIGA), progression-free survival was identical in African-American men compared with Caucasians. Surprisingly, PSA declines and the durability of this response was much greater in African-American patients. What is unique about these two studies is the investigation of racial differences in advanced prostate cancer outcomes in the era of newer therapeutic options.

These studies, both based on clinical trial participation, suggest that some African-American men with advanced disease may actually possess characteristics that make them respond better. With these two trials engaged in ongoing molecular analysis of some of their cohorts, genomic and single nucleotide polymorphism analysis should provide further insight into the optimum management and safety profiles of these advanced prostate cancer therapies.

Previous studies that have identified unique biomarkers with significant differences in expression by ethnicity suggest there may be different molecular pathways that lead to the development of prostate cancer. These differing pathways may also be found to impact response to advanced prostate cancer therapy in different races.

These two studies may not provide insight into the primary causes of the racial disparities in prostate cancer. However, they do provide hope that when treated for advanced prostate cancer, the outcomes in African-Americans appear to be at least as good, if not better, than other ethnicities.