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Long-Term Colorectal-Cancer Mortality after Adenoma Removal
28 August 2014
Oslo University Hospital
Patients with intestinal polyps have a lower risk of dying from cancer than previously thought, according to Norwegian researchers. The Norwegian study is the world’s largest of its kind.
Although colonoscopic surveillance of patients after removal of adenomas is widely promoted, little is known about colorectal-cancer mortality among these patients.
Using the linkage of the Cancer Registry and the Cause of Death Registry of Norway, we estimated colorectal-cancer mortality among patients who had undergone removal of colorectal adenomas during the period from 1993 through 2007. Patients were followed through 2011. We calculated standardized incidence-based mortality ratios (SMRs) using rates for the Norwegian population at large for comparison.
Norwegian guidelines recommended colonoscopy after 10 years for patients with high-risk adenomas (adenomas with high-grade dysplasia, a villous component, or a size ≥10 mm) and after 5 years for patients with three or more adenomas; no surveillance was recommended for patients with low-risk adenomas. Polyp size and exact number were not available in the registry. We defined high-risk adenomas as multiple adenomas and adenomas with a villous component or high-grade dysplasia.
We identified 40,826 patients who had had colorectal adenomas removed. During a median follow-up of 7.7 years (maximum, 19.0), 1273 patients were given a diagnosis of colorectal cancer. A total of 398 deaths from colorectal cancer were expected and 383 were observed, for an SMR of 0.96 (95% confidence interval [CI], 0.87 to 1.06) among patients who had had adenomas removed. Colorectal-cancer mortality was increased among patients with high-risk adenomas (expected deaths, 209; observed deaths, 242; SMR, 1.16; 95% CI, 1.02 to 1.31), but it was reduced among patients with low-risk adenomas (expected deaths, 189; observed deaths, 141; SMR, 0.75; 95% CI, 0.63 to 0.88).
After a median of 7.7 years of follow-up, colorectal-cancer mortality was lower among patients who had had low-risk adenomas removed and moderately higher among those who had had high-risk adenomas removed, as compared with the general population. (Funded by the Norwegian Cancer Society and others.)