Story highlights "Bad luck" of stem cell mutation is not the primary cancer risk factor, says a new study the journal Nature

Environmental and lifestyle factors, which can be modified, are "large risk proportions for cancer," it says

A study earlier this year concluded that heredity and environment could be blamed for only some of the risk

(CNN) The greater majority of cancer may be influenced by environment and lifestyle factors.

That's what the authors of a new study in the journal Nature argue. External factors such as exposure to toxins and radiation are a major risk factor in developing cancer, the new study says.

"Environmental factors play important roles in cancer incidence and they are modifiable through lifestyle changes and/or vaccination" the authors write.

Looking at the increasing incidences of various types of cancers, including lung cancer, the authors concluded that "large risk proportions for cancer are attributable to changing environments" such as smoking and air pollutants. Exposure to the sun and poor diet play a role.

This has been widely known among scientists, and might sound like the advice you hear from your doctor. But what this study does is build upon a conversation about how cancer starts and why there is some variability in the kinds of cancers.

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