Insufficient evidence regarding the optimal screening strategy for this population means that a number of published screening recommendations exist differing in the definition of risk, type and frequency of tests recommended, and the age at which individuals should start screening. There has been a lack of evidence for a specific screening strategy in the moderate risk population. Although it is currently widely published that people at moderate-risk of CRC be referred for colonoscopy at five-yearly intervals starting at age 50 yrs (or ten years younger than the age of the earliest diagnosis of CRC in the family, whichever comes first), there is a lack of evidence for this specific age cut-off. A UK study shows that colonoscopy every 5 years from age 25 yrs decreases mortality in the moderate-risk group by 81%. However, the risk of cancer or high-risk polyps under the age of 45 yrs is low (less than 5%).r
Although flexible sigmoidoscopy or CT colonography may be considered if colonoscopy is contra-indicated, as yet there is insufficient evidence of reduction in CRC incidence or mortality to recommend either method for routine screening.r There is no specific data for moderately-increased risk groups.
Considerable evidence supports the effectiveness of aspirin as risk-reducing medication for CRC in high-risk Lynch syndrome patients (>50% reduction in CRC risk).r
Long term (>10 years) and regular use of aspirin has been associated with a 19% reduction in cancer of the colorectum in a population-wide study.r This association was not modified by gender, age or family history of cancer and other disease and lifestyle factors. However, there is insufficient cost-benefit data to recommend aspirin as risk-reducing medication for CRC in the general population.
There is no specific evidence for the moderate risk group.
Modifiable lifestyle risk factors for bowel cancer
For a summary of the evidence for modifiable lifestyle risk factors for CRC, see NHMRC “Clinical Practice Guidelines for the Prevention, Early Detection and Management of Colorectal Cancer”^, supported by Australian data from the Melbourne Colorectal Cancer Study.r These recommendations apply to the general population; there is no specific evidence for the moderate-risk group.
^NHMRC “Clinical Practice Guidelines for the Prevention, Early Detection and Management of Colorectal Cancer” (2005) Reference number: CP106 (Guidelines and Summary: Section 1, page xv and Chapter 2: Primary Prevention, page 8-31).