The majority of cancers are caused by lifestyle and environmental factors such as smoking, drinking alcohol and air pollution, a new study has found.
The research findings contradict a study from earlier this year, that found differences in cellular processes to be the cause of certain tissues becoming cancerous.
This led scientists to believe that many cancers were merely a case of "bad luck" and were unavoidable.
However the new study suggested that most cancers could actually be prevented with lifestyle changes.
Yusuf Hannun, a cancer researcher at Stony Brook University in New York, was interested in how external factors such as radiation affect stem division rates.
Along with his team, Hannun studied how environmental factors contributed to cancer risk. He analysed data which showed, for example, that people who migrated from regions of lower cancer risk to those with higher risk soon developed disease at rates consistent with their new environment.
They also looked at patterns in the mutations associated with certain cancers.
Hannun and his team found that mutations during cell division rarely build up to the point of producing cancer, even in tissues with relatively high rates of cell division.
In almost all cases, the team found that some exposure to environmental factors would be needed to set off the disease.
Professor Kevin McConway from The Open University told The Telegraph: "For many common types of cancer, this study concludes that at least 70% to 90% of the cancers are due to external risk factors – roughly speaking, that 70% to 90% would not occur if we could magic away all the risk factors.
"Even if someone is exposed to important external risk factors, of course it isn’t certain that they will develop a cancer – chance is always involved.
"But this study demonstrates again that we have to look well beyond pure chance and luck to understand and protect against cancers."
But Dr Helen Webberley, the dedicated GP for Oxford Online Pharmacy, said the study should be taken with a pinch of salt.
"We have known for a long time that bad habits cause cancer, but we do need to be careful about how we interpret this research, otherwise we would all stay at home wrapped in cotton wool," she said.
"There are obviously some very clear associations between cancer and environmental and external factors, and the biggest is smoking.
"We know that the nasty skin cancers - the melanomas - can be induced by sun exposure at a younger age. And as a doctor I have no hesitation in saying that nobody should smoke, and we should all be careful in the sun.
"However, with other factors such as alcohol, red meat, cooking oils, number of children, air pollution - it is all about moderation. I wouldn't want people to vastly change their habits out of the fear of developing cancer."
She concluded: "Eat and drink sensibly, make positive lifestyle choices, consider your diet and exercise patterns with care. But yes, do not smoke. Ever."
The study was published in the journal Nature.
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