The risk of colorectal cancer (CRC) in ulcerative colitis (UC) increases with extent and duration of disease. Identifying other risk factors would allow targeting of sub-groups at greatest risk, enabling more cost-effective surveillance.


We conducted a case-control study comparing 102 cases of CRC in UC with matched controls. Odds ratios (OR) for cancer risk were estimated by conditional logistic regression. A multivariate model assessed the contribution of individual variables.


Regular 5-aminosalicylic acid (5-ASA) therapy reduces cancer risk by 75% (OR 0.25, 95% CI: 0.13–0.48, P < 0.00001). Adjusting for other variables, taking mesalazine regularly reduces risk by 81% (OR 0.19, 95% CI: 0.06–0.61, P=0.006) and visiting a hospital doctor more than twice a year also reduces risk (OR 0.16, 95% CI: 0.04–0.60, P=0.007). Considering variables independently, having a family history of sporadic CRC in any relative increases risk fivefold (OR 5.0, 95% CI: 1.10–22.82, P < 0.04).


CRC risk among UC patients can be reduced by regular therapy with 5-ASA medication. Colonoscopic surveillance may be best targeted on those unable to take 5-ASAs (e.g. due to allergy) and those with a positive family history of CRC.