The bowel cancer trifecta for Australian men - and how small changes can slow it
Being overweight, drinking too much and having a history of smoking is the perfect trifecta to raise risk of bowel cancer, through the roof, for men.
A big data study involving 370,000 Australians has shown this potent trifecta will be responsible for over one in three bowel cancer cases among males in the next decade.
The trifecta is far less harmful in women and is likely to be responsible for just one in eight cases.
This startling gender difference suggests more resources should go into encouraging men over 50 with these risk factors to use the free bowel cancer test that arrives in their mail box every two years.
While smoking, body fatness and over-drinking are known risk factors for bowel cancer, the unique aspect of this research is it shows how the combination of all three, in one individual, can be devastating.
It suggests if men with all three risk factors, modified at least one, they could reduce their risk.
"We don't expect anyone to stop all three at once, but if they can make small changes, they may well see a significant difference," says study leader, Associate Professor Claire Vajdic, Head of the Cancer Epidemiology Research Unit at UNSW's Centre for Big Data Research in Health.
"Behavioural change is very hard and the evidence shows small manageable changes can produce a benefit and that often, this can snowball and reinforce behavioural change."
Significant results
Big data studies have limitations but the results from this research are significant enough to influence public policy.
Currently, projections show the trifecta will be responsible for 36,000 preventable cases of bowel cancer in Australian men over the next decade and 11,000 in women.
Published in the journal JNCI Cancer Spectrum, the research is the first to identify subgroups within the Australian population with the highest risk burden of this cancer.
It revealed an interplay between smoking and alcohol with the burden attributable to a smoking history being significantly exacerbated by excessive alcohol consumption, and vice-versa.
"This means the future bowel cancer burden would be markedly lower if current and former smokers did not drink excessive alcohol."
The research showed the burden relating to smoking persists for four decades after quitting, reinforcing the importance of preventing smoking initiation and encouraging smoking cessation.
That smokers over 50 are less likely to participate in the National Bowel Cancer Screening Program, increases their vulnerability to this disease.
The research, which pooled results from seven cohort studies (cohort studies identify a population exposed to a particular factor and follows them over time), found 11 per cent of the future bowel cancer burden can be attributed to ever-smoking, and 4 per cent to current smoking.
What about meat?
Overweight or obesity was responsible for 11 per cent of cases, and excessive alcohol consumption contributed 6 per cent of the burden.
"Combined, these factors will be responsible for one in four future bowel cancers in men and women," Professor Vajdic says.
"We found more bowel cancers were caused by overweight or obesity and excessive alcohol consumption in men than in women."
Men tend to be heavier and drink more. This, together with differences in hormonal factors and in body fat distribution, are likely to be driving factors.
Unfortunately, there was not sufficient data available for the study to include the high consumption of red and processed meats, which constitutes a big risk factor for bowel cancer.
The risk has been well-demonstrated in other studies and, in future, meat could change the trifecta into a quadrella.
"With obesity, smoking and drinking, meat is the barbecue stopper for Australian culture," Professor Vajdic says.
