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A new biomarker, which is under investigation at Johns Hopkins, shows great potential to address both of these controversial issues.
Early research indicates that a serum assay based on this marker, known as Early Prostate Cancer Antigen-2 (EPCA-2), is both highly sensitive and specific (see, "New marker may be more specific for prostate Ca"). PSA's sensitivity for prostate cancer is in the range of 70%, and its specificity is approximately 64%. By comparison, the figures for EPCA-2 are 94% and 97%, respectively, according to the Hopkins research, led by Robert H. Getzenberg, PhD. While other markers for prostate cancer have been studied, none has demonstrated such high sensitivity and specificity.
The current data on EPCA-2, which need to be validated in larger numbers of patients and at multiple institutions, suggest its potential role in a number of important clinical applications.
Second, a serum assay for EPCA-2 could potentially help urologists determine tumor stage and an appropriate choice of treatment, since the initial research has shown that patients with localized disease do, in fact, have lower levels of EPCA-2 than do patients with either locally advanced or metastatic disease.
Third, if elevated levels of EPCA-2 in the serum are confined to prostate cancer patients and are higher in those with advanced disease, then this new marker may also be able to separate patients who have indolent disease from those with progressive disease.
Fourth, if the gene sequence that codes for EPCA-2 is determined, the potential would exist for identifying patients at risk for the disease-and possibly developing a prevention strategy to use before it actually occurs.
While these applications hold great promise, much more research is needed before they become reality.
Richard D.Williams, MD
Dr. Williams, a Urology Times editorial consultant, is professor and chair, department of urology, University of Iowa, Iowa City.