Systematic review with meta-analysis: the declining risk of colorectal cancer in ulcerative colitis

Background Patients with ulcerative colitis (UC) have an increased risk of developing colorectal cancer (CRC); however, the magnitude of this effect is open to debate. Aim To assess the risk of CRC in UC patients by systematic review and meta-analysis. Methods A systematic literature search was performed up to November 2013. We selected studies describing the incidence and prevalence of CRC in patients with UC. Articles were assessed for quality using the Newcastle-Ottawa Scale. Cumulative incidence and incidence rates of CRC were combined and analysed using the generic inverse variance method. Sub-analyses were performed to identify factors associated with an increased risk of developing CRC. Results A total of 81 studies (181923 patients) met the inclusion criteria. The incidence rate of CRC in patients with UC was 1.58 per 1000 patient-years (py) [95% confidence interval (CI), 1.39-1.76]. Results were heterogeneous (I-2=81-89%). The incidence rate was 4.02/1000 py (95%CI=2.74-5.31) in studies that only included patients with extensive colitis, and 1.24/1000 py (95%CI=1.01-1.47) in population-based studies. The incidence rate was 0.91/1000 py (95%CI=0.61-1.2) in the first decade of disease, 4.07/1000 py (95%CI=2.58-5.56) in the second, and 4.55/1000 py (95%CI=2.64-6.46) in the third. The incidence rate decreased from 4.29/1000 py in the studies published in the 1950s to 1.21/1000 py in studies published in the last decade. Conclusions The risk of patients with ulcerative colitis developing colorectal cancer has decreased steadily over the last six decades, but the extent and duration of the disease increase this risk.