Getting Cancer is Really Just 'Bad Luck'

Scientists have long believed that lifestyle choices were the root causes for getting cancer, but now new research indicates that it's really just to blame on good ole fashioned "bad luck."

According to a statistical model created by scientists from the Johns Hopkins Kimmel Cancer Center, two-thirds of adult cancer cases are caused by random DNA mutations that occur when stem cells divide. The remaining third are due to environmental factors and inherited genes.

"All cancers are caused by a combination of bad luck, the environment and heredity, and we've created a model that may help quantify how much of these three factors contribute to cancer development," researcher Bert Vogelstein said in a statement.

"Cancer-free longevity in people exposed to cancer-causing agents, such as tobacco, is often attributed to their 'good genes,' " he added, "but the truth is that most of them simply had good luck."

But that's not to say that lifestyle choices and habits aren't as important when it comes to getting these fatal diseases. But rather, scientists behind the study say the focus should be more on early detection and treatment instead of trying to prevent cancer.

Cancer occurs when tissue-specific stem cells make random mistakes, or mutations, meaning one chemical letter in DNA is incorrectly swapped for another during the replication process in cell division. And the more mutations, the higher the cancer risk.

Until now, scientists didn't know how much of a part these mutations played in cancer incidence, that is, in comparison to the contribution of hereditary or environmental factors. So the team charted the number of stem cell divisions in 31 tissues and compared these rates with the lifetime risks of cancer in the same tissues among Americans.

"Our study shows, in general, that a change in the number of stem cell divisions in a tissue type is highly correlated with a change in the incidence of cancer in that same tissue," Vogelstein explained.

For example, colon tissue undergoes more stem cell divisions than tissue in the small intestine, which is why, researchers say, colon cancer is more common than small intestine cancer.

What's more, they found that 22 cancer types could be largely explained by the "bad luck" factor of random DNA mutations. However, predictably big name cancers like lung cancer, skin cancer and forms of cancers associated with hereditary syndromes have more to do with environmental and inherited factors than with simple bad luck.

The scientists are also quick to note that breast and prostate cancer were not included in this research.

The findings are described in more detail in the journal Science.

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