Patients with ulcerative colitis (UC) have an increased risk of developing colorectal cancer (CRC). Studies examining the magnitude of this association have yielded conflicting results. We performed a meta-analysis of population-based cohort studies to determine the risk of CRC in patients with UC.

We used MEDLINE, EMBASE, Cochrane, and CINAHL to perform a systematic literature search. We included 8 studies in the meta-analysis on the basis of strict inclusion and exclusion criteria. We calculated pooled standardized incidence ratios (SIRs) with 95% confidence intervals (CIs) for risk of CRC in patients with UC and performed meta-regression analyses of the effect of cohort size, calendar period, observation time, percentage with proctitis, and rates of colectomy on the risk of CRC.

An average of 1.6% of patients with UC was diagnosed with CRC during 14 years of follow-up. SIRs ranged from 1.05 to 3.1, with a pooled SIR of 2.4 (95% CI, 2.1–2.7). Men with UC had a greater risk of CRC (SIR, 2.6; 95% CI, 2.2–3.0) than women (SIR, 1.9; 95% CI, 1.5–2.3). Young age was a risk factor for CRC (SIR, 8.6; 95% CI, 3.8–19.5; although this might have resulted from small numbers), as was extensive colitis (SIR, 4.8; 95% CI, 3.9–5.9). In meta-regression analyses, only cohort size was associated with risk of CRC.

In population-based cohorts, UC increases the risk of CRC 2.4-fold. Male sex, young age at diagnosis with UC, and extensive colitis increase the risk.