More-Accurate Blood Test for Prostate Cancer

A recently identified blood protein may change the way men are tested for prostate cancer. Testing for this protein may curtail unnecessary biopsies and differentiate disease that has spread outside the prostate (metastases) from cancer within the prostate.

Early prostate cancer antigen-2 (EPCA-2) is the second prostate-cancer marker identified by Professor Getzenberg and colleagues at the James Buchanan Brady Urological Institute at The Johns Hopkins University School of Medicine (Baltimore, MD, USA). Last year, they described an unrelated tissue-based test, EPCA-1, that also proved effective in identifying prostate cancer. The only commonality between these markers is that they were discovered using the same approach.

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 ml of PSA are considered at risk for prostate cancer. However, PSA testing often highlights noncancerous conditions (false-positives) and can miss some cases of cancer (false-negatives).

In a study to be published in the online August 24, 2006, issue of the journal Lancet, Professor Getzenberg and his team proposed that EPCA-2 testing is a more accurate way to identify prostate cancer. They measured EPCA-2 levels in the blood of 330 Johns Hopkins patients separated into several groups. Results showed that the EPCA-2 test was negative in 97 % of the patients who did not have prostate cancer. Men with no evidence of disease (regardless of their PSA levels), as well as the control group of patients with other cancer types and benign conditions, had EPCA-2 levels below the cutoff level.

Ninety percent of the men with organ-confined prostate cancer and 98 % of the men with disease outside of the prostate had EPCA-2 levels at or above the cutoff level. Overall, the EPCA-2 test detected 94 % of the men with prostate cancer. In addition, EPCA-2 levels were significantly higher in patients whose cancers had spread outside of the prostate compared to those with disease confined to the gland. EPCA-2 was much better at separating these groups than PSA levels.

"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,” said Professor 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.” Larger clinical trials for EPCA-2 are planned that could make this test available to the public in approximately 18 months.



Related Links:
James Buchanan Brady Urological Institute at The Johns Hopkins University School of Medicine