Background: The risk of colorectal cancer (CRC) in ulcerative colitis (UC)
increases with extent and duration of disease. Identifying other risk facto
rs would allow targeting of sub-groups at greatest risk, enabling more cost
-effective surveillance.
Methods: 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 contribu
tion of individual variables.
Results: 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 varia
bles, taking mesalazine regularly reduces risk by 81% (OR 0.19, 95% CI: 0.0
6-0.61, 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 incr
eases risk fivefold (OR 5.0, 95% CI: 1.10-22.82, P < 0.04).
Conclusions: CRC risk among UC patients can be reduced by regular therapy w
ith 5-ASA medication. Colonoscopic surveillance may be best targeted on tho
se unable to take 5-ASAs (e.g. due to allergy) and those with a positive fa
mily history of CRC.