New Blood Test for Prostate Cancer Showing Promise

April 27, 2007— Testing for a blood protein researchers are calling early prostate cancer antigen (EPCA)-2 may overcome some of the limitations of current practices. While screening for prostate-specific antigen (PSA) has been the standard of care for more than 2 decades, it is not specific for prostate cancer, and raised concentrations have been linked to other prostate conditions such as benign prostatic hyperplasia and prostatitis. Several groups have been working to identify new biomarkers for prostate cancer, and this latest effort, published in the April issue of Urology, shows that EPCA-2 has potential as a new serum-based test.

Due to elevated PSA levels, an estimated 1.6 million men undergo prostatic biopsies in the United States every year. Approximately 80% of these patients have negative results, reports a news release about the study. Conversely, about 15% of men with prostate cancer go undetected because their PSA levels are below the cutoff level.

EPCA-2 is the second prostate-cancer marker identified by the same researchers that has outperformed PSA. Last year, the team identified a tissue-based test, EPCA-1, that also proved effective in flagging prostate cancer. The only similarity between these markers is that they were discovered using the same approach. The efficacy of EPCA-1 as a test of biopsy samples is currently being studied.

Improved Early Detection and Reduced False Positives Compared With PSA Testing

"A blood test based on EPCA-2 may greatly improve our ability to accurately detect prostate cancer early, minimize the number of false positives, and lower the number of unnecessary biopsies," senior author Robert Getzenberg, PhD, from the Brady Urological Institute at Johns Hopkins Hospital, in Baltimore, Maryland, told reporters. "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 the gland."

Under a licensing agreement between Onconome Inc and the University of Pittsburgh and Johns Hopkins, Dr. Getzenberg is entitled to a share of royalties received by the university on sales of products described in this paper. Dr. Getzenberg is also a paid consultant to Onconome. The terms of this arrangement are being managed by Johns Hopkins in accordance with its conflict-of-interest policies.

The current study was supported by a grant from the National Institutes of Health, National Cancer Institute, and Onconome. The group, led by Eddy Leman, PhD, also at Hopkins, measured EPCA-2 levels in 330 patients separated into several groups:

Men with normal PSA levels and no evidence of disease.
Men with elevated PSA levels who had negative biopsies.
Men with benign prostatic hypertrophy 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 spread outside the gland at the time of surgery.
A diverse group of patients with benign conditions of other organs as well as those with other cancer types.
Patients with an EPCA-2 cutoff level of 30 ng/mL 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. The researchers found that EPCA-2 had 92% specificity (95% CI, 85% – 96%) for healthy men and those with benign prostatic hyperplasia and 94% sensitivity (95% CI, 93% – 99%) for overall prostate cancer. The specificity for PSA in these groups of patients was only 65% (95% CI, 55% – 75%).

The investigators report, "The results of our study have shown that EPCA-2 is a novel biomarker associated with prostate cancer that has high sensitivity and specificity and accurately differentiates between men with organ-confined and non–organ-confined disease." Dr. Getzenberg says larger clinical trials for EPCA-2 are planned that could make this test available in about 18 months.

Urology. 2007;69:714-720.

Source: http://www.medscape.com/viewarticle/555789?src=mp