Two new studies offer conflicting views on the value of screening men for prostate cancer using the prostate-specific antigen (PSA) test. The two studies found that the popular PSA blood test, used to screen for prostate cancer, save few lives and lead to risky and unnecessary treatments for large numbers of men.

According to an article in the New York Times the findings the first test of PSA based on large, randomized populations confirm longstanding concerns about the wisdom of widespread prostate cancer screening. Although the studies are ongoing, results so far are considered significant and the most definitive to date.

High levels of PSA, a protein released by prostate cells, suggests that cancer might be present, prompting physicians to order biopsies to determine if cancer exists inside the gland. It has been difficult to determine, however, whether finding prostate cancer early saves lives. Most prostate cancers tend to grow very slowly and are never a threat, particularly in older men. And no clear test is available to distinguish between the faster-growing cancers and the slow ones, resulting excessive and often unnecessary surgical treatment .

"The reported European and U.S. studies are far from surprising," says Dr. Amnon Gonenne, President and CEO of Mabcure Inc., a diagnostic company that has developed through its proprietary hybridoma technology a series of highly specific monoclonal antibodies (MAbs) against melanoma, ovarian carcinoma, and prostate cancers. "Many doctors feel that the PSA test is over-subscribed in the U.S. compared to Europe. The notion that PSA is not useful for diagnosing prostate cancer or saving patients lives has been around for quite some time."

Dr. Gonenne notes other clinical studies that previously uncovered serious flaws with PSA testing. "On one hand, it has a very significant error in accurately diagnosing patients with prostate cancer, with up to 75% false positives; on the other, it may miss identifying many patients who actually have cancer up to 20% false negatives."

The severe limitations of PSA testing stems from the fact that the antigen is not a true cancer marker, but a surrogate for an enlarged or otherwise inflamed prostate. These conditions, known as benign prostate hyperplasia, occur quite frequently among men over fifty years of age. Some prostate cancers are associated with prostate inflammation but many other are not.

"Since the majority of prostate cancers are not life threatening, most men, depending on their age, are likely to die with the disease rather than from the disease," says Dr. Gonenne. "Therefore, the challenge of diagnosing prostate cancer in its early stage is not merely identifying the presence of cancer, but the ability to determine if the cancer is indolent and therefore of low risk, or aggressive and life threatening. Until prostate cancer-specific markers are identified the diagnostic challenge of identifying men at risk will not be met."

Help on the Horizon

A blood prostate exam that can help identify life-threatening cancer is on the horizon thanks to novel science using monoclonal antibodies (MAbs). MAbs are large, highly complex proteins that recognize other molecules or regions of other molecules known as antigens.

MabCure's scientists have created proprietary MAbs using hybridomas, a hybrid cell that is a cross between antibody-producing immune system cells and a myeloma (blood or bone marrow cancer). Hybridoma cells possess the antibody-generating ability of immune system cells and the "immortality" of cancer cells. This means hybridomas multiply indefinitely, churning out MAbs during most of their lifecycle. Without hybridoma technologies creating large quantities of monoclonal antibodies (MAbs) would be impossible.

MabCure Inc. is creating MAbs for the detection of cancer (in blood, urine, or other bodily fluids) at an early stage, where the cure rates are greater than 90%. "At least one of our MAbs has been shown to have high specificity in that it does not react with normal prostate tissue but only with diseased one," says Dr. Gonenne. "MabCure plans to expand its MAb repertoire as well as screen its anti-prostate cancer MAbs for their ability to detect early aggressive cancer in serum or urine." For more information, log on to mabcure.

Mabcure, Inc.
mabcure