The report from Cancer Research UK released this week says up to 90 percent of cancer cases are not caused by DNA or genetics, but outside factors like lifestyle and environment.
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In 2012, there were nearly 339,000 of new cancer cases of cancer recorded and nearly 162,000 deaths, according to figures from Cancer Research UK. In a study published in Nature, a team of statisticians and cancer biologists describes four lines of evidence – mathematical, epidemiological, and molecular – that undermine the idea that most cancers are the result of random biological mistakes.
Yusuf Hannun, a cancer researcher at Stony Brook University in NY, wondered about the effect of external factors such as radiation on stem cell division rates.
Giles Hooker from Cornell University in NY, said the findings were based on a “very simplified model of cancer mutation” and the numbers “should at best be regarded as ballpark estimates”.
Meanwhile, only 10 to 30 percent were caused by intrinsic risk factors – processes that result in random DNA mutations. Now, using genome sequencing, we can see the contribution of germline mutations to pediatric cancer risk.
The conclusion evoked some criticism from the scientific community, and now new findings from the Stony Brook researchers assert that the vast majority of cancers – approximately 70 to 90 percent – stem from environmental exposure and individual behaviours.
Ironically, given the brickbats that flew when the “bad luck” study was published in January, that paper’s authors don’t really disagree.
In support of the findings of the research, Kate Allen from World Cancer Research Fund, said that it was a major breakthrough that proved cancers can also be prevented.
Third, the team also analyzed the SEER (Surveillance, Epidemiologic, and End Results Program) data, which showed that many cancers have been increasing in incidence and in mortality, suggesting that external factors contribute heavily to these cancers. They noted that immigrants who move from a country with a low incidence of tumours to another with a higher incidence were at greater risk of developing cancer.
“But this study demonstrates again that we have to look well beyond pure chance and luck to understand and protect against cancers”. In those cases, they argued, early detection and treatment would be more effective than prevention. They found that when three or more mutations are required for cancer onset (which is a now accepted parameter), intrinsic factors are far from sufficient to account for the observed risks, indicating small percentages of intrinsic cancer risks in many cancers.
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“This paper marks an important turning point in our understanding of pediatric cancer risk and will likely change how patients are evaluated”, said corresponding author James R. Downing, MD, St. Jude president and chief executive officer.
