MEDICUS FEBRUARY 2016

R E S E A R C H

and family history, to name a few. With so many variables driving risk, it is clear no two people are likely to have exactly the same risk profile. Another way of communicating this issue came from our friends at Cancer Research UK. Out of every 1,000 people in the UK, about 61 will develop bowel cancer at some point in their lives. Those who eat the lowest amount of processed meat are likely to have a lower lifetime risk than the rest of the population (about 56 cases per 1,000 low meat-eaters). If you only expect to live to 65, your chance of getting bowel cancer is 2.9 per cent if you don’t eat processed meat and 3.4 per cent if you eat 50 grams each day. Of course, if you go with bacon and eggs for breakfast, a heaped ham sandwich at lunch and a big antipasto plate as a dinner entrée, the risk increases, but to similar proportions for each additional 50 grams per day. Absolute risks allow people to personalise the effects and to better compare them. Yes, calculating absolute risk requires a strong assumption that there are no other differences between people who are exposed and not exposed. But surely being able to compare absolute risks is more informative and less likely to mislead than relative risks. We might also talk about the population attributable fraction – that is, the fraction of cancer that is due to the risk factor. Professor David Whiteman and team at QIMR in Brisbane recently estimated that 18 per cent of bowel cancers

in Australia could be attributed to consumption of red and processed meat.³ Due to an absence of data they did not separate the effects of processed and red meat. They estimated that about 2,600 cases of cancer in Australia in 2010 were attributed to red and processed meat consumption. A lot of public money, via taxes or donated funds to cancer organisations, is invested in research. There is a moral imperative to report the findings of such research, but rarely is one study definitive. The challenge is to get the message across as simply and accurately as possible. AMA (WA) members will know that challenge only too well. The work of IARC is vital to bring together the best assessment of the evidence about what does and does not contribute to cancer risk. And people want to know. The best cancer is the one you never get. Given we know the cause of about one-third of cancers in Australia⁴

(smoking, alcohol, sun exposure, lack of exercise and nutrition factors), it is not unreasonable to give the best available information to people about what we know. But clearly we have a way to go in better communicating what these risks really mean, their relative scale and importance, and how people can use this information in their daily choices. Luckily, decades of solid evidence underpins some pretty simple advice to stack the cancer odds in our favour. While this may be a gross simplification and medical professionals have the challenge of personalising this to the circumstances of individuals and patients, for most people:

• DO MORE: physical activity, eating fruit and vegetables

• DO LESS: drink alcohol, eat high- calorie food, processed and probably red meat, expose skin to intense sunlight

• DON’T: smoke. ■

References available on request.

Terry Slevin is Education and Research Director at the Cancer Council WA and Adjunct Professor in the Health Science Faculty at Curtin University. This piece was adapted from a piece written jointly with Professor Dallas English for The Conversation .

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