An experimental blood test has detected prostate cancer so accurately that it could supplant PSA levels as a screening mechanism for the disease, according to researchers.
Investigators at Johns Hopkins University in Baltimore discovered an early prostate cancer antigen (EPCA-2) that functions as a biomarker. In a sample of 330 men, EPCA-2 levels identified 94% of those who had prostate cancer and 97% of the patients who did not. It also differentiated between cancers that were confined to the prostate gland and those that had metastasized.
The sample included men with:
- Normal PSA levels and no evidence of disease.
- Normal PSA levels and prostate cancer.
- Elevated PSA levels but who had negative biopsies.
- Benign prostatic hyperplasia (BPH) who did not receive biopsies for prostate cancer.
The EPCA-2 test identified 78% of men who had prostate cancer with PSA levels below 2.5 ng/mL. In addition, three quarters of the BPH patients had a level of EPCA-2 below the cutoff point of 30 ng/mL.
Lead investigator Robert H. Getzenberg, PhD, director of research at the James Buchanan Brady Urological Institute at Johns Hopkins, says this result was significant because BPH is often associated with elevated PSA levels, leading to misdiagnosis.
“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,” he says.
The researchers found levels of EPCA-2 were highest in men whose cancer had spread beyond the prostate, making it dramatically easier to detect advanced disease than PSA tests allow. “This is im-portant, since cancer that has spread outside the prostate is more deadly, which makes it even more crucial to have a tool that detects it early,” Dr. Getzenberg says.
He is planning a larger clinical trial and estimates that the test could be approved for general use in about 18 months.
The study was funded by the National Cancer Institute of the National Institutes of Health and Onconome, Inc., a biotechnology company based in Seattle. Dr. Getzenberg, who holds a patent for the test, works for Onconome as a paid consultant and will receive royalties when the test becomes commercially available.