Colorectal cancer incidence is low in patients following a colonoscopy

Colonoscopy has been proven a valuable tool in preventing colorectal cancer in controlled studies; we conducted a longitudinal confirmation study in everyday clinical practice.

In a retrospective study, we monitored the outcome of patients with a total colonoscopy at our hospital between 1994 and 2007. We analysed the data of in-house follow-up colonoscopies, a national person registry and the morphological tumour registry centralizing all histopathological data at a national level. Patients with a particular colorectal cancer risk were excluded.

8950 patients were included in our study. 2032 (22.7%) patients had at least one colorectal adenoma at index colonoscopy. Adenoma prevalence was significantly higher in men than in women (27.9% vs. 17.4%, p<0.001) and was increasing with age in both sexes. Patients were followed for a mean of 5.2 years and 19 had invasive colorectal cancer detected over 47,725 person years of follow-up. The incidence rate was 0.40 cases/1000 person years of follow-up (95% confidence interval, 0.25-0.62), and the standardized incidence ratio was 0.37 (95% confidence interval, 0.24-0.58).

Incidence rates of colorectal cancer are low in the follow-up of patients having undergone a total colonoscopy in everyday practice. After standard therapy of colorectal adenomas at colonoscopy, there is little evidence for excess colorectal cancer incidence in this subgroup.