African American men with Gleason score 3+3=6 prostate cancer produce less prostate-specific antigen (PSA) and have significantly lower PSA density (PSAD) than white men, according to a new study published in The Journal of Urology (doi:10.1016/j.juro.2015.08.089). These findings could have important implications when deciding whether active surveillance is appropriate for a patient with prostate cancer.

Prostate cancer is the second leading cause of cancer death among men in the United States, with nearly 30,000 deaths annually. According to the latest recommendations by the American Urological Association, PSA is the only screening test for men with unremarkable findings on digital rectal examination in whom prostate biopsy should be considered.

Prostate cancer-specific deaths have declined by approximately 40% since the advent of PSA screening in the late 1980s, and 40% to 70% of that decline may be attributable to screening. For early-stage low-grade disease, active surveillance, commonly called watchful waiting, is considered appropriate.

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Although race was identified as a contributing risk factor for prostate cancer in prior studies, Oleksandr N. Kryvenko, MD, assistant professor of Pathology and Urology at Sylvester Comprehensive Cancer Center at the University of Miami Miller School of Medicine in Florida and lead investigator of this study, explains that “Active surveillance criteria that were predictive in Caucasian men were not accurate in African American men. Despite this finding, active surveillance criteria do not include race as a variable.”

In this study, the investigators measured tumor volume from consecutive radical prostatectomies in 414 men (348 white, 66 African Americans) with low-risk prostate cancer, based on National Comprehensive Cancer Network criteria. They compared clinical presentation, pathological findings, PSA, PSAD, and PSA mass (PSAM; an absolute amount of PSA in a patient’s circulation) between African American and white men.

This study revealed that African American men with Gleason score 3+3=6 prostate cancer produce less PSA than white men. Serum PSA and PSAM were equal in the two groups of men despite African American men having significantly larger prostates (approximately 10 g larger); all other parameters, particularly total tumor volume, were the same. PSAD was approximately 20% lower in African American men compared with white men, even when tumor volume was the same.

“When low volume and low-grade cancer is detected, especially in older individuals, the decision between active surveillance and definitive therapy must be made,” commented Kryvenko.

“Because PSAD was about 20% lower in African American men even with the same tumor volume as in Caucasians, this finding could be one of the factors why current active surveillance criteria in African Americans are not as accurate as those for Caucasians. A lower PSAD threshold for active surveillance inclusion criteria in African American men may account for these differences.”

Kryvenko explained that cancer in African American men is found to be a higher grade at radical prostatectomy. Furthermore, the spatial distribution of their cancers is concerning in that standard prostate biopsies may undersample more aggressive tumor nodules. Therefore, a constellation of factors explain why contemporary surveillance criteria do not work well in African American men.