Wednesday, August 10, 2011

Prostate Cancer and the Single Biomarker

As per my last post, biomarkers have a key role to play in biotechnology and medicine. It is also becoming clear that more than one biomarker in a diagnostic test is better, or a combination of biomarkers may be even better. There is always room for tweaks and improvements, as diagnostic tests are as much an art (and a lot of luck) as science.  Take the case of prostate cancer­­. Prostate-specific antigen (PSA) has become an accepted, if not foolproof, biomarker for testing for prostate cancer. Using a scale and environmental factors (patient’s family history, age etc.), doctors use PSA to help determine if the cancer warrants more aggressive treatment. However, PSA is not perfect. There is a risk of false positives—perhaps too many for comfort. These false results have led to unnecessary biopsies and other costly, invasive treatments and tests. Despite its less than perfect track record, PSA is still a useful tool on the whole. 

There is clearly a need for more biomarkers to work in tandem with PSA or on their own.   Prostate cancer is the leading cause of cancer for men in the United States, with 223,000 new cases reported a year, according the Centers for Disease Control. (This is based on 2007 statistics which are the most recent numbers available, according to both the American Cancer Society and the Centers for Disease Control.) At the moment, however, we are using a similar “throw the spaghetti on the wall” approach for everyone.  

There are several new biomarkers on the horizon for prostate cancer. Most are still in the early stages but some are moving along from academia into validation. For example, PCA3 is a gene that is over-expressed in prostate cancer cells and was identified by a group of researchers at Johns Hopkins in June of this year. Since PCA3 is only detected when there is prostate cancer in the body, it is currently thought that a urine test is all that will be necessary to detect its presence.Yesterday, a group of researchers from the University of Cleveland and Harvard University published a study in the British Journal of Cancer.  The group has discovered a biomarker, GSTP1, which boosts the efficacy of the PSA test. GSTP1 is more sensitive in detecting the difference between benign prostate troubles and prostate cancer than PSA. Like PCA3, it can be identified via a urine or blood test.

 Public and private companies also continue to make headway in this area. Some are still in early stages, some in the key validation phase. Tests that run the gamut—using one or two biomarkers to full assay panels with many markers—are expected to launch in 2012 and 2013.These tests are hoping to go one step better than “just” PSA. (For a brief sampling, read this.)

It is clear that biomarkers, in prostate and other cancers will continue to move along.
As investors, scientists and doctors, we are impatient to see the promise of biomarkers pay-off. Now, the possibility of a growing light in the tunnel—and one that is not attached to a speeding freight train fueled by wasted R&D dollars—is here.

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