Many of today's tools for screening and diagnosing cancer are crude at best. So researchers are working to find more-sensitive tests based on specific molecules --  called "biomarkers"  --  that are early signs of tumors and whose concentration could, ideally, be measured in bodily fluids like blood.

While much of that research has focused on protein biomarkers, some of the first molecular tests to arrive on the market may be ones that look instead at a phenomenon called DNA methylation. A few small biotech companies, some partnered with major pharmaceutical companies like Johnson and Johnson and Roche, say their first DNA methylation-based tests for prostate cancer could be available next year.