Lifestyle behaviors and environmental factors account for
around 70-90% of cancer cases, consistent with new
research published within the journal
Researchers say up to 90% of cancer cases are caused by lifestyle and environmental factors, like smoking.
The study contradicts a study published within the journal Science in January, which suggested the bulk of cancer cases are right down to “bad luck.”
In that study, Johns Hopkins researchers claimed 65% of cancer cases are a results of random DNA mutations, while the remaining 35% of cancer cases are explained by a mixture of those mutations and environmental and hereditary factors.
The research spurred much debate, with many scientists arguing against the “bad luck” theory.
Intrinsic factors ‘account for 10-30% of cancer cases’
One approach was an analysis of tissue cell turnover, which involved assessing the quantitive relationship between the lifetime risk surely cancers – like pancreatic, lung and colorectal cancers – and division of normal tissue stem cells.
Fast facts about cancer
There will be around 1,658,370 new cancer cases diagnosed within the US this year
Around 589,430 cancer deaths will occur within the US. Breast cancer remains the foremost common cancer in women, while prostatic adenocarcinoma is that the commonest cancer for men.
The researchers explain that if intrinsic risk factors
– that’s , processes that end in random DNA mutations – played a key role in
cancer development, then the entire number
of divisions in tissue stem cells would correlate with lifetime cancer risk.
However, they found this pattern was uncommon, with intrinsic factors only accounting for around 10-30% of cancer cases. “In summary, regardless of whether a subpopulation or all dividing cells contribute to cancer, these results indicate that intrinsic factors don’t play a serious causal role,” say the authors.
Another approach involved mathematical analysis of recent studies on mutational cancer signatures – defined as “‘fingerprints’ left on cancer genomes by various mutagenic processes.”
The team identified 30 distinct signatures among different cancers, and that they analyzed these signatures to work out the extent to which they were triggered by intrinsic or extrinsic factors – like lifestyle and environment.
From this, the researchers found that the majority cancers – including lung, colorectal, bladder and thyroid cancers – possessed large numbers of mutations that were likely to possess been caused by extrinsic factors; only a couple of cancers had large proportions of intrinsic mutations, consistent with the team.
Additionally, the researchers found strong epidemiological evidence supporting the high contribution of extrinsic factors to cancer development. for instance , an analysis of immigrants who moved from countries with low cancer incidence to those with high cancer incidence revealed these individuals quickly acquired a better cancer risk, suggesting extrinsic factors were responsible .
‘People can’t hide behind bad luck’
The team says their overall findings indicate that lifestyle and environmental factors account for around 70-90% of cancer cases, while intrinsic factors account for around 10-30% – findings that highly contradict those of the Science study.