New Prostate Cancer Biomarkers Can Predict Aggressive Disease in African Americans

It is well-known that African-American men have a higher incidence of prostate cancer and a greater mortality rate than American men of other races and ethnicities. Evidence from previous studies has identified several biomarkers that can predict aggressive types of prostate cancer; however, these studies have included mainly European-American men and did not focus on ethnicity as an important variable.

Kosj Yamoah, MD, PhD, Radiation Oncology, Moffitt Cancer Center, Tampa, FL, and colleagues, have now investigated the relevance of these various biomarkers to the identification of aggressive prostate cancer and disease recurrence in African-American men with prostate cancer (Yamoah K, et al. J Clin Oncol. 2015;33:2789-2797).

Study Details

The study included 154 African-American and 243 European-American men with prostate cancer. The patients were identified from 4 US institutions and were matched based on their Cancer of the Prostate Risk Assessment Postsurgical (CAPRA-S) score at diagnosis; all were matches within 2 points of one another. The median follow-up time was 39 months.

Of all the biomarkers identified in previous studies, only the 20 biomarkers that have been reported twice or more to be associated with aggressive prostate cancer were evaluated in this study. To determine a potential ethnically dependent association between biomarkers and disease status that can predict the risk for pathologic (p)T3 prostate cancer in an “ethnicity-dependent manner,” the researchers looked for a significant ethnic difference by biomarker interaction, with P <.05 predicting the risk for clinicopathologic outcomes.

Significant Differences Among Ethnic Groups

The use of the Mann-Whitney-Wilcoxon test to examine continuous biomarker expression levels in a patient showed significant differences in expression by ethnicity in 6 biomarkers—ERG, AMACR, SPINK1, NKX3-1, GOLM1, and androgen receptor. In addition, a logistic regression model used to assess differences based on ethnicity showed significant differences among the 2 ethnic groups in 4 biomarkers—ERG, AMACR, SPINK1, and GOLM1.

The results also showed that African-American men are diagnosed with prostate cancer at an earlier age (range, 37-73 years) than European-American men (range, 43-76 years), and they are also more likely to have triple-negative disease than European-American men.

According to Dr Yamoah and colleagues, “One of the more striking findings was the ethnic association between pT3 disease and ERG” among African-American men, as well as their increased risk for the triple-negative prostate cancer subtype. The investigators added that these findings indicate that prostate cancer “may arise from different tumor progenitors and/or distinct molecular pathways” in European-American and African-American men.

This is the largest and only study to identify prostate cancer biomarkers that can predict the risk for adverse clinical outcomes in specific ethnic groups. The results show a physiologic difference in the expression of prostate cancer biomarkers in African-American men versus European-American men.

Understanding these ethnic differences can influence the approach to the diagnosis and treatment of African-American men with prostate cancer, and can reduce current differences in outcomes for this patient population.