Nine in 10 cancers caused by lifestyle, not genes: study

Environmental and external factors such as smoking, drinking, sun exposure and air pollution may account for up to nine out of 10 cancers, a new study has claimed.

It was previously believed that random cell mutations played a significant role in the development of tumours, researchers said.

However, scientists at the Stony Brook University in New York now believe that outside influences have a far greater impact, meaning many cancers may be more preventable than previously thought.

The researchers said that cancer incidence is far too high to be explained away by simple mutations in cell division, 'The Telegraph' reported.

"Here we provide evidence that intrinsic risk factors contribute only modestly to cancer development. The rates of mutation accumulation by intrinsic processes are not sufficient to account for the observed cancer risks," said Yusuf Hannun of Stony Brook University.

The researchers looked at previous studies which have shown how immigrants moving from low cancer incidence to countries with high cancer incidence soon develop the same tumour rates, suggesting the risks are environmental rather than biological or genetic.

"For many common types of cancer, this study concludes that at least 70 per cent to 90 per cent of the cancers are due to external risk factors – roughly speaking, that 70 per cent to 90 per cent would not occur if we could magic away all the risk factors," said Kevin McConway from the Open University in the UK.

According to the new research, nearly 75 per cent of the risk of colorectal cancer is now believed to be due to diet.

As many as 86 per cent of the risk of skin cancer is due to sun exposure while 75 per cent of chance of developing head and neck cancers is because of tobacco and alcohol, researchers said.

Although some rare cancers can be driven by genetic mutations, the most prevalent diseases are down to environmental factors, researchers said, adding that it is important that these 'extrinsic' factors are taken into account in cancer prevention and research.

The finding is likely to prove controversial as it suggests that people could slash their risk of ever getting cancer if they just made lifestyle changes such as keeping out of the sun, exercising or cutting down on cigarettes, researchers said.

The findings were published in the journal Nature.