Cancer is often found when someone starts to feel symptoms—pain, an abnormal growth, or maybe just fatigue. Now scientists have developed a computer program that could identify and locate cancer even before symptoms arise, opening the door for earlier screening and better treatment.The program, called CancerLocator, detects tumor DNA in patient blood samples, and precisely pinpoints where the tumor is located in the body. In a small pilot study, it successfully diagnosed liver, lung, and breast cancer in 80 percent of cases, giving researchers hope that the program could eventually be used as part of regular health checks, eliminating the need for invasive biopsies.Developed by researchers from the University of California, Los Angeles, and the University of Southern California, CancerLocator works by analyzing DNA that escapes into the bloodstream when cells die. Each fragment of DNA has a unique pattern of chemical add-ons, called methyl groups, that mark which genes were turned on or off. These methyl markers can indicate whether a gene was interrupted in a cancerous cell. And because different cells and tissues have different genes that are activated in the body, the methylation patterns can also act as a blueprint for where the DNA comes from."It's very much like a message in a bottle," says Jasmine Zhou, a professor of pathology at the University of California, Los Angeles, and co-lead author of the study. "This cell-free DNA floating in the blood can tell us the secrets of each cell or organ that it's from."So far, only one FDA-approved test is available that uses this type of free-floating tumor DNA, and it relies on fecal samples, not blood. Other non-invasive screening methods test for intact tumor cells that are loose in the bloodstream. But finding intact tumor cells in blood often only gives an indication of cancer prognosis and is like searching for the proverbial needle in a haystack.Read the full story on Motherboard.