For years, the PSA test, which measures prostate-specific antigen (a protein produced by the prostate gland) levels in the blood, has been used to screen men for prostate cancer. When the prostate gland enlarges for any reason, including conditions such as infection or cancer for example, the PSA levels tend to rise. If the PSA level is 4 or above, prostate cancer is suspected and a biopsy is performed.

The researchers found that "the genetic influence [on PSA levels] is fairly subtle," explains Sue Ann Ingles, PhD, assistant professor of preventive medicine at the Keck School of Medicine at the University of Southern California (USC) in Los Angeles, and principal author of the study.

"If a man is having his PSA level tested, I don’t think genetics are going to be a big influence on the results," continues Ingles. "We were trying to determine what is influencing PSA production and nobody has ever looked at genetics as a possible influence."

Ingles and her colleagues evaluated 420 men of various ethnic backgrounds between the ages of 45 and 75. None of the participants had ever been diagnosed with prostate cancer. The men were evaluated by looking at blood and urine samples in the laboratory, in addition to detailed health and diet surveys. Genetics appeared to influence PSA levels only slightly across all of the populations.

The authors also indicate that the importance PSA plays in a man’s risk of developing prostate cancer is still not fully understood.

"Although the PSA has been used as a tumor marker for many years, the role of PSA in prostate physiology is still unclear," they write. "The effects of [the PSA] in prostate cancer risk have been controversial," adds co-author Gerhard Coetzee, PhD, a molecular biologist and associate professor of urology, preventive medicine and microbiology at University of Southern California.

Coetzee also commented that, in the broader picture, adding genetic factors into the equation can only help in providing a better understanding of the disease and how prostate cancer is diagnosed and treated. "Knowledge of your genetic risk can make a big difference in how you treat the disease ultimately," states Coetzee.

Herman Kattlove, MD, MPH, a medical oncologist and medical editor for the American Cancer Society agrees.

"This study suggests that in the future, we’re going to have more information than just the PSA about who may be susceptible to prostate cancer," says Kattlove. "The PSA level of 4 these days is the dividing point to determine who should have a biopsy, but the problem is that many of these biopsies come back negative — those men do not have cancer, but yet there are others who have PSAs below 4 who do have cancer," says Kattlove.

"Having other markers, such as these genetic analyses, in addition to the PSA will help us better decide who should have a biopsy," he says.