What are the factors increasing the risk of developing bowel cancer?
- Tobacco smoking: the risk is increased by 38% for every 40 cigarettes smoked per day. Approximately 8.0% of all bowel cancer in UK is attributable to tobacco consumption.
- Obesity and abdominal fatness: there is an increased risk of 3%, 5% and 3% per inch in waist circumference for colorectal, colon and rectal cancer. Individuals who gain over 20Kg in weight after the age of 20 have a 38% higher risk of bowel cancer.
- Red and processed meat consumption: there is a 17% increase in risk per 100 gm of red meat and 24% increase in risk per 50 gm of processed meat consumed. Processed food in general may also contribute to an increased risk.
- Alcohol consumption: there is a 10% increase in risk per 10gm of alcohol consumed per day.
- Physical inactivity and sedentary behaviour: there have been studies linking increasing amounts of screen time to an increased risk of bowel cancer.
- It has been estimated that in the adult white population in the US that 60% of bowel cancer for men and women could be prevented by lifestyle factors.
What can be done to decrease risk of death from bowel cancer?
- Ideally all patients need to be counseled to modify their risk factors as outlined above. They should maintain a healthy weight, take regular exercise (30-60 minutes of moderate exercise per day), cease smoking and reduce alcohol to no more than 2 standard drinks per day for a male. A healthy diet that is low in processed meats and saturated animal fats and and high in fibre will help reduce risk. This information is relevant to all age groups but the earlier this advice is delivered the better.
- In the US recommendations from the USPSTF (US Preventive Services Task Force) have recommended reducing the age of screening to 45. This is currently not recommended in Australia as modelling suggested a marginal cost effective benefit. While screening of the general population under the age of 50 is not recommended in Australia currently, it would seem reasonable to offer screening with the immunochemical FOBT from age 40 to those identified (ie those with risk factors outlined above) as being at higher risk. Note that screening with colonoscopy is not recommended for this age group and does not attract a rebate under current Medicare guidelines.
- The American College of Gastroenterology does recommend diagnostic evaluation of colon and rectum for all patients, irrespective of age, who present with symptoms consistent with bowel cancer, including but not limited to, rectal bleeding, change in bowel habit, iron deficient anaemia and abdominal pain. In the past there may have been a tendency to ascribe these symptoms in younger patients to benign diseases such as haemorrhoids or fissures.
- Current NHMRC advice in Australia recommends that aspirin (100 mg/day) be actively considered in average risk patients over the age of 50 to help prevent development of bowel cancer. While it is not currently recommended in the under 50s it would seem reasonable to consider it in the higher risk groups. Aspirin should be avoided in patients with uncontrolled hypertension and those with helicobacter pylori infection.
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