A new study in the Journal of Urology reveals that African-American men have an antigen profile that differs from Caucasians, and the current prostate-specific antigen (PSA)-based screening may exclude men in this racial group who should be included in prostate cancer surveillance programs.

For early stage low-grade prostate disease, surveillance of disease progression — so-called watchful waiting — is common practice. Screening PSA levels to identify and place men on watchful waiting have reduced death from prostate cancer by 40% since screening programs were initiated in the 1980s.

PSA is also the only available test to select subjects for prostate biopsy with unremarkable results from a digital rectal examination. In this study, however, Dr. Oleksandr N. Kryvenko from the University of Miami, and colleagues show that current PSA cut-off values are not suitable for African-Americans.

The study included 348 whites and 66 African-Americans, and compared clinical presentation, pathological findings, PSA, PSAD, and PSA mass (PSAM) — an absolute amount of PSA in a patient’s circulation — between these two groups.

The study showed that when comparing men with same-size tumors, African-Americans produced less PSA and had a lower PSA density (PSAD) score than Caucasians. Likewise, the groups had equal levels of serum PSA and PSAM despite the significantly larger prostates, indicating more advanced disease, found in African-American men.

The team concluded that all other factors being equal, African-Americans have on average a 20% lower PSAD than Caucasians.

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

He added that the new findings complement his earlier study, also published in The Journal of Urology. “African Americans overall not only have a higher grade cancer at radical prostatectomy, but also, their spatial distribution of cancer in prostate is such that standard prostate biopsy may undersample more aggressive tumor nodules. Thus, there could be a constellation of factors explaining why contemporary surveillance criteria do not work well in African American men.”