Cancer patients often wonder "why me?" Does their tumor run in the family? Did they try hard enough to avoid risks like smoking, too much sun, or a bad diet? Lifestyle and heredity get the most blame, but new research suggests random chance plays a bigger role than people realize: Healthy cells naturally make mistakes when they multiply, unavoidable typos in DNA that can leave new cells carrying cancer-prone genetic mutations, reports the AP. In fact, about two-thirds of the mutations that occur in various forms of cancer are due to those random copying errors, researchers at Johns Hopkins University explain in a study published in Science. That doesn't mean most cases of cancer are due solely to "bad luck," though.
It takes multiple mutations to turn cells into tumors—and a lot of cancer is preventable, the Hopkins team stressed, if people take proven protective steps. But it should help with the "why me" question from people who have "done everything we know can be done to prevent cancer but they still get it," says study author Bert Vogelstein. Vogelstein and statistician Cristian Tomasetti analyzed mutations involved in 32 types of cancer to estimate that 66% of the gene flaws are due to random copy errors. Environmental and lifestyle factors account for another 29%, while inherited genes made up just 5%. Which is the most common factor differs by cancer, the team says. Estimates from Britain suggest 42% of cancers are potentially preventable with a healthy lifestyle, and the Hopkins team says their mutation research backs that idea. (Read more cancer stories.)