New Cancer Study

Striking back at an earlier paper that seemed to suggest that cancer is due to “bad luck” a new study demonstrates the powerful role of lifestyle on cancer development.  From the news story:

Most researchers agree cancer is likely caused by the body's stem cells dividing at uncontrollable rates. A study published in the journal Science back in January appeared to show two-thirds of cancer types were victims of bad luck, or chance mutations.

But a new study, which included some of the same data as the January study, argues only as much as 30 percent of cancers fall under the so-called "bad luck hypothesis."

Instead, the main causes were found to be external. Causes include diet, alcohol and cigarette use, sunburns, viruses, pollution and more –– including some factors that haven't been identified yet. The director of Stony Brook Cancer Center, from the university that conducted the study, told the BBC if intrinsic risk is like Russian roulette, "... then maybe one in six will get cancer. Now, what a smoker does is add two or three more bullets to that revolver. And now, they pull the trigger." The researchers noted in their paper at least nine other studies have shown evidence against the "bad luck hypothesis," but they say theirs is the first to quantitatively appraise the relative contribution of extrinsic factors. The finding could significantly alter how cancer is both treated and prevented.

The paper is here. This is the abstract:
 

Recent research has highlighted a strong correlation between tissue-specific cancer risk and the lifetime number of tissue-specific stem-cell divisions. Whether such correlation implies a high unavoidable intrinsic cancer risk has become a key public health debate with the dissemination of the ‘bad luck’ hypothesis. Here we provide evidence that intrinsic risk factors contribute only modestly (less than ~10–30% of lifetime risk) to cancer development. First, we demonstrate that the correlation between stem-cell division and cancer risk does not distinguish between the effects of intrinsic and extrinsic factors. We then show that intrinsic risk is better estimated by the lower bound risk controlling for total stem-cell divisions. Finally, we show that the rates of endogenous mutation accumulation by intrinsic processes are not sufficient to account for the observed cancer risks. Collectively, we conclude that cancer risk is heavily influenced by extrinsic factors. These results are important for strategizing cancer prevention, research and public health.

And their important conclusion:

…a consistent estimate of contribution of extrinsic factors of > 70–90% in most common cancer types. This is consistent with the overall conclusion regarding the role of extrinsic factors in cancer development.

Therefore, the important actionables remain consistent for cancer prevention: a healthy diet, avoid smoking, and get sufficient physical activity.