A Good Biomarker Is Hard to Find

Are cancer biomarkers all they're cracked up to be? Not always, writes Monica Desai in the Guardian's science blog. Of the thousands of biomarkers researchers are aware of, only a small percentage of them is being used in the clinic to find treatments for disease. There have been successes like HER-2 in breast cancer which led to the formulation of Herceptin, Desai says, but not every biomarker turns out to be as useful. For every HER-2, there's a PSA, which doctors thought could be a way of detecting prostate cancer, but soon found is present in non-cancerous prostates as well. "So what's the problem with these biological fingerprints? Why are they proving difficult to use?" Desai asks. For one thing, some of the molecules being discovered aren't specific to one type of cancer — some proteins are present in different cancers in different organs. Another problem, Desai adds, is that the tests used to measure biomarkers can be faulty, missing cancer or give false positive readings. While cancer biomarkers are promising, and researchers are developing new technologies to detect and use them, the biomarkers themselves aren't acting in isolation, Desai writes. "Carry on reading those headlines, but do it with lots of pinches of salt," she says.