A Better Blood Test for Prostate Cancer

New studies of a blood protein recently identified at Johns Hopkins, early prostate cancer antigen-2 (EPCA-2), may change the way men are screened for prostate cancer - a disease that kills tens of thousands of men every year.

Current standards of screening and testing for prostate cancer focus on the blood protein prostate-specific antigen (PSA) along with a digital rectal examination. Men who have more than 2.5 nanograms per milliliter of PSA are considered at risk for prostate cancer. However, PSA testing often erroneously highlights noncancerous conditions (false positives) and can miss some cases of cancer (false negatives), according to Robert H. Getzenberg, Ph.D., professor of urology and director of research at the James Buchanan Brady Urological Institute at The Johns Hopkins University School of Medicine.

Due to elevated PSA levels, approximately 1.6 million men undergo prostatic biopsies in the United States annually, and roughly 80 percent of these men have negative results, according to Getzenberg, lead author of the study. He says that of the entire population of men in the United States who have been tested for PSA, an estimated 25 million have elevated PSA levels and a biopsy of the prostate that did not reveal any prostate cancer. Conversely, roughly 15 percent of men with prostate cancer go undetected because their PSA levels are below the cutoff level, according to Getzenberg.

In a study published in the April issue of the journal Urology, Getzenberg and a team of Hopkins researchers introduce evidence in support of EPCA-2 testing as a more accurate way to identify cancer in the prostate.

“A blood test based on EPCA-2 may greatly improve our ability to accurately detect prostate cancer early and minimize the number of false positives, therefore lowering the number of unnecessary biopsies,” says Getzenberg. “In addition, this is the first time we have a test that effectively distinguishes between men with cancer confined to the prostate and those whose disease has spread outside of the gland.”

Getzenberg and his team measured EPCA-2 levels in the blood of 330 Hopkins patients separated into several groups: men with normal PSA levels and no evidence of disease; men with elevated PSA levels but who had negative biopsies, men with a common noncancerous prostate condition known as benign prostatic hypertrophy (BPH) who did not receive biopsies for prostate cancer, men with prostate cancer but with normal PSA levels, men with prostate cancer confined to the prostate, men with prostate cancer that had invaded outside of the gland at the time of surgery, and a diverse group of patients with benign conditions of other organs as well as individuals with other cancer types.

Patients with an EPCA-2 cutoff level of 30 nanograms per milliliters or higher were considered to be at risk for prostate cancer. This cutoff was based on a pilot study of 30 blood samples, which was then applied throughout the larger study.