Most cancer cases due to lifestyle choices, not 'bad luck,' study suggests

Between 70 and 90 percent of cancer cases are linked to avoidable lifestyle choices like exposure to radiation and toxic chemicals, suggests a study published online Wednesday in the journal Nature.

That conclusion, drawn from researchers at Stony Brook University in New York, adds to ongoing study of the causes of cancer and individuals’ ability to reduce their risk. It also challenges findings published in the journal Science earlier this year that suggested most cancer cases are primarily due to “bad luck.”

Johns Hopkins University researchers made the previous observation after studying the interaction between stem cell divisions and cancer risk in various tissues. They determined that— independent of lifestyle choices and known cancer risks— the more those divisions occurred, the higher the individual’s cancer risk would be. Researchers argued that some cancers were clearly linked to lifestyle choices— like lung cancer and smoking— but that for other cancers, the stem cell division and cancer risk relationship still existed regardless of those choices.

“What they did was interesting, but I was startled by the conclusion,” Yusuf Hannun, a cancer researcher at Stony Brook University and author of the new paper, said in a Nature news release.

Hannun and his team set out to re-examine that notion by analyzing mathematical models, epidemiological data, and cancer cell mutation patterns. They concluded that mutations during cell division rarely resulted in cancer— even in tissues with relatively high rates of cell division, according to the news release. And, they wrote, in nearly all of the disease instances, some level of exposure to environmental factors, like carcinogens, was necessary to trigger cancer.

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While Johns Hopkins mathematician Cristian Tomasetti, a study author for the Science paper, argued that the  Stony Brook study doesn’t account for certain characteristics of tumor growth, other specialists welcomed the new findings as they encourage cancer prevention efforts.

“By not smoking, your lifetime risk of lung adenocarcinoma drops dramatically,”  Edward Giovannucci, who studies cancer prevention at the Harvard T. H. Chan School of Public Health and wasn’t involved in either study, said in the news release. “The fact that your risk of pelvic sarcoma is even lower because there’s less stem-cell division— so what?”