Epidemiology and risk factors for colorectal dysplasia and cancer in ulcerative colitis.

Patients with UC are at increased risk of CRC, but a series of population-based studies published within the past 5 years suggest that this risk has decreased over time. The crude annual incidence rate of CRC in UC ranges from approximately 1 in 500 to 1 in 1600. In some cohorts, an elevated risk of CRC relative to the general population can no longer be demonstrated. The exact mechanism for this decrease in risk remains unclear but may be attributable to a combination of more widespread use of maintenance therapy and surveillance colonoscopy as well as more judicious reliance on colectomy. In addition to the classic risk factors of increased extent and duration of UC, it seems that PSC, a family history of sporadic CRC, severity of histologic bowel inflammation, and young age at colitis onset are independent risk factors for cancer.