Which of the following statements regarding the risk of cancer in the context of ulcerative colitis is/are correct?

b. After 10 years of active disease, the risk of cancer approximates 2% to 3%

 Significant dysplasia or suspected colon cancer is a clear indication for colectomy in patients with ulcerative colitis. Earlier studies have suggested that the risk of cancer is relatively low for the first ten years after the onset of disease activity (roughly 2% to 3%). The incidence of colon cancer then begins to climb at a rate of 1% to 2% per year. By the time the patient has had ulcerative colitis for 20 years, the risk of colon cancer approximates 20%. Many epidemiologists believe that earlier studies overestimated the risk of malignancy due to referral bias and the imperfection of retrospective surveys performed in tertiary referral hospitals.