Posted on February 6th, 2009 by
Men who have elevated levels of prostate-specific antigen (PSA) are often referred for a prostate biopsy in order to determine whether they have prostate cancer. Men who have a negative first biopsy, however, are often still uncertain about their risk of prostate cancer; since a biopsy only samples small areas of the prostate, it’s not uncommon for a repeat biopsy to detect cancer that was missed by the first biopsy. In order to remove this uncertainty, there is interest in developing tests that can distinguish between those who truly do not have prostate cancer and those who do (in spite of a negative biopsy).
The field of proteomics offers promising developments in this area. Proteomics is the study of proteins, which are the functional units of cells. Prostate cancer researchers have identified a protein called Early Prostate Cancer Antigen, or EPCA, that is found throughout the prostate in men with prostate cancer—even in areas that appear normal.
The fact that EPCA is present in areas of the prostate that do not yet have cancer makes this a particularly interesting protein. It suggests that tissue from a negative prostate biopsy could be tested for EPCA; the presence of the protein would suggest that the man had prostate cancer even though the biopsy was negative. Similarly, men without EPCA could be reassured that they most likely do not have prostate cancer.
EPCA Displays Accuracy
A study that assessed the use of EPCA testing in men with negative prostate biopsies reported that EPCA was highly accurate in identifying prostate cancer.
The study applied the EPCA test to two sets of prostate tissue: one set from organ donors who did not have prostate cancer and one set from men with prostate cancer. When applied to the organ donors without prostate cancer, the test correctly classified 85% as cancer-free. When applied to the negative biopsies of the men subsequently found to have cancer, the test correctly classified 84% as having cancer.
These results are particularly encouraging because the negative biopsies had taken place up to five years before the cancer diagnosis—this means EPCA testing of negative biopsy tissue could lead to earlier identification and treatment of prostate cancer.
The identification of EPCA as a marker for prostate cancer makes this an exciting time for researchers, physicians and, most importantly, for patients and their families. New tests made possible by emerging technologies are likely to provide improved screening tools for prostate cancer, reduce the number of unnecessary biopsies, and help patients and their doctors make important medical decisions.
The EPCA test, called ProstaMark®, was developed by the Seattle-based company, Tessera. It became available in mid-August 2005.
1) Dhir R, Bietmeier B, Arlotti J et al. Early identification of individuals with prostate cancer in negative biopsies. The Journal of Urology. 2004;171:1419-1423.
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Tags: Prostate Cancer
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