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.