NEW YORK, United States, Tuesday December 22, 2015 – Earlier this year, researchers sparked a debate by suggesting that random cell mutations, rather than lifestyle choices, played a significant role in the development of tumours, a finding dubbed the “bad luck hypothesis.”
A new study has nevertheless led scientists to believe that external influences have a far greater impact, implying that many cancers may be more preventable than previously thought.
The latest finding suggests that people could slash their risk of ever getting cancer if they just made lifestyle changes such as quitting smoking, cutting back on alcohol, adopting a healthier diet, exercising and reducing sun exposure.
The Telegraph reports that the new research follows on from a study published in January, which suggested that 65 percent of cancers were inevitable and driven by random mistakes in cell division which are completely outside of our control.
The more cells divide, the greater the chances that a mutation can occur, leading to cancer, Johns Hopkins University said, and claimed it explained why areas of the body where cell division occurred more quickly, such as the colon, were more likely to develop tumours.
The new study, by Stony Brook Cancer Centre in New York, nevertheless suggests that cancer incidence is far too high to be explained away by simple mutations in cell division.
Dr Yusuf Hannun, the director of Stony Brook, said: “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.”
The new study, published in the journal Nature, used four approaches to conclude that only 10-30 percent of cancers were caused by the way the body naturally functions or “luck.”
BBC News reports that the team of doctors from Stony Brook approached the problem from different angles, including computer modelling, population data and genetic approaches.
The results consistently suggested 70-90 percent of the risk was due to extrinsic factors, they said.
Dr Hannun told the BBC News website: “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.
“It is like a revolver, intrinsic risk is one bullet.
“And if playing Russian roulette, then maybe one in six will get cancer – that’s the intrinsic bad luck.
“Now, what a smoker does is add two or three more bullets to that revolver. And now, they pull the trigger.
“There is still an element of luck as not every smoker gets cancer, but they have stacked the odds against them.
“From a public health point of view, we want to remove as many bullets as possible from the chamber.”
The researchers also noted previous studies which have shown how immigrants moving from low cancer incidence countries to countries with high cancer incidence soon develop the same tumour rates, suggesting the risks are environmental rather than biological or genetic.
Nearly 75 percent of the risk of colorectal cancer is now believed to be due to diet.
Similarly, 86 percent of the risk of skin cancer is down to sun exposure while 75 per cent of chance of developing head and neck cancers is due to tobacco and alcohol, according the new research.
Although some rare cancers can be driven by genetic mutations, the most prevalent diseases are down to environmental factors, they conclude. They say it is important that these “extrinsic” factors are taken into account in cancer prevention and research.
It was previously thought that fewer than half of cancer could be prevented by lifestyle changes, but the new research indicates that it could be much higher.
Kevin McConway, Professor of Applied Statistics at The Open University, said research provided “pretty convincing evidence” that external factors play a major role in many cancers.
“For many common types of cancer, this study concludes that at least 70 percent to 90 percent of the cancers are due to external risk factors – roughly speaking, that 70 percent to 90 percent would not occur if we could magic away all the risk factors,” he said.
“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.”