Nine in ten cancers caused by lifestyle, says new study

A new study has found that environmental and external factors such as smoking, drinking and air pollution are the likely cause of the majority of cancer cases.

The study, by doctors from Stony Brook Cancer Centre in New York, was published in the journal Nature. It used four new approaches to determine that only 10 to 30 per cent of cancers were down to the way the body naturally functions or to 'luck'.

Cancer is caused by one of the body's cells dividing out of control. There has been some debate as to the role external factors play in causing this accelerated division.

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Earlier this year, researchers caused controversy by suggesting that two thirds of cancer types were down to luck rather than external factors, but the new study disagrees.

"External factors play a big role, and people cannot hide behind bad luck," Dr Yusuf Hannun, the director of Stony Brook, told the BBC.

"They can't smoke and say it's bad luck if they have cancer – not every smoker gets cancer, obviously there is still an element of luck, but they have stacked the odds against them."

Doctors have warned that not all external factors that cause cancer have been identified and not all of them may be avoidable.

"The finding is likely to prove controversial," says the Daily Telegraph, "as it suggests that people could slash their risk of ever getting cancer if they just made simple lifestyle changes."

But experts have described the evidence as "pretty convincing".

Kevin McConway, a professor of applied statistics at the Open University, said: "They do provide pretty convincing evidence that external factors play a major role in many cancers, including some of the most common.

"This study demonstrates again that we have to look well beyond pure chance and luck to understand and protect against cancers."

Around 330,000 people are diagnosed with cancer in the UK each year and 161,000 will die, according to statistics from Cancer Research UK.