Not just bad luck: Most cancer cases caused by environment & lifestyle choices, new study says

Cancer cells are seen on a large screen connected to a microscope at the CeBit computer fair in Hanover. © Fabian Bimmer
Cancer is among the leading causes of death worldwide, but a new study says developing the disease isn't all down to bad luck. In fact, it claims that between 70 and 90 percent of cancer cases are linked to avoidable lifestyle choices.

The study, conducted by researchers at Stony Brook University in New York and published on Wednesday in the journal Nature, was launched in response to previous research which stated that most cancer cases were primarily due to “bad luck.”

That study, conducted by Johns Hopkins University researchers in January, left cancer researcher Yusuf Hannun seeking more information.

“What they did was interesting, but I was startled by the conclusion,” Hannun said in a Nature news release.

Hannun and his team decided to launch their own study, which involved analyzing mathematical models, epidemiological data, and cancer cell mutation patterns.

They found that in nearly all the disease instances analyzed, some level of exposure to environmental factors, such as carcinogens, was necessary to trigger cancer. Ultraviolet (UV) radiation and smoking were found to be other avoidable risks.

The scientists concluded that such external factors contribute to between 70 to 90 percent of cancers.

"External factors play a big role, and people cannot hide behind bad luck. They can't smoke and say it's bad luck if they have cancer...there is still an element of luck as not every smoker gets cancer, but they have stacked the odds against them,” Hannun told BBC.

Meanwhile, only 10 to 30 percent were caused by intrinsic risk factors – processes that result in random DNA mutations.

"In summary, irrespective of whether a subpopulation or all dividing cells contribute to cancer, these results indicate that intrinsic factors do not play a major causal role," the authors stated.

The team also found that environment was important, noting that people who migrated from regions of lower cancer risk to areas with higher risk soon developed the disease at rates consistent with their new environment.

The scientists concluded that the findings show “cancer risk is heavily influenced by extrinsic factors,” adding that the results “are important for strategizing cancer prevention, research, and public health.”