The total lifetime risk for colorectal cancer (CRC) in patients with ulcerative colitis (UC) was comparable to that observed in the general population, according to results of a Norwegian cohort study published in BMJ Open Gastroenterology.

The IBSEN cohort is a population-based inception cohort of patients diagnosed with inflammatory bowel disease between 1990 and 1993 in Norway. IBSEN enrollees underwent follow-up visits at 1, 5, 10 and 20 years following UC diagnosis. All visits included a clinical examination, structured, interview, and laboratory tests. Surveillance colonoscopies were performed in indicated patients. The present analysis included IBSEN enrollees who were diagnosed with UC at any point during follow-up. The primary outcome was presence of CRC. Patients who developed CRC prior to UC diagnosis were excluded from statistical analyses. Researchers modeled the risk for CRC using Cox proportional hazard regression. They adjusted regression models for gender, UC severity and duration, age at UC diagnosis, concurrent diagnosis of primary sclerosing cholangitis, and family history of CRC. The researchers compared CRC rates in the UC cohort with rates in the background population, estimated using data from the Cancer Registry of Norway.

A total of 517 patients with UC were included in analyses, of whom 255 were men. Median age at UC diagnosis was 40 (range, 25-62) years. Median follow-up time was 20.4 years. The cumulative incidence of CRC at 20-year follow-up was 1.6% (8 of 517 patients). The total lifetime risk for developing CRC either before or after UC diagnosis was 2.3% (12 of 517 patients).

In patients diagnosed with CRC after UC, median age at CRC diagnosis was 56 (range, 39-88) years. In risk analyses, older age at UC diagnosis was associated with increased risk for CRC. Specifically, patients who were aged >70 years at UC diagnosis were significantly more likely to develop CRC than patients who were aged <40 years (HR, 15.68; 95% CI, 1.31-187.92). Gender, colitis severity, concurrent primary sclerosing cholangitis, and having a first-degree relative with CRC did not appear to affect CRC risk in the UC cohort.

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The total lifetime risk for CRC in the background population of Norway was estimated at 2.8% in women and 3.1% in men. These rates are higher than those observed in the UC cohort. Possible explanations for this discrepancy include the anti-inflammatory effects of UC medication and the increased regularity of screening colonoscopies in the UC population.

Compared with the background population, risk for CRC was low in patients with UC. Older age at UC diagnosis was associated with significantly increased risk for CRC. The small incidence of CRC in the UC cohort limited the statistical power of risk factor analyses. “The power of the study did not allow us to conclusively evaluate the association between CRC and previously established risk factors,” investigators wrote. “[Continued follow-up of the IBSEN cohort] is necessary for a more precise estimation of the possible risk factors.”

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Reference

Klepp P, Brackmann S, Cvancarova M, et al. Risk of colorectal cancer in a population-based study 20 years after diagnosis of ulcerative colitis: results from the IBSEN study. BMJ Open Gastroenterol. 2020;7(1):e000361