Risk of advanced metachronous colorectal adenoma during long-term follow-up

According to the adenoma-carcinoma concept, all colorectal adenomas are to be removed and all patients have to undergo regular surveillance examinations. But there is still shortage on information on the long-term results of follow-up colonoscopy after polypectomy.

Between 1978 and 2003, more than 20,000 polyps were prospectively documented at the Erlangen Registry of Colorectal Polyps. A total of 1,091 patients undergoing periodic surveillance examinations are studied for differences between initial and metachronous lesions of the colorectum. Statistical analysis using chi (2)-testing of adenoma characteristics found in four subsequent recurrence periods and calculation of the relative risk (RR) for the development of metachronous adenomas of advanced pathology was performed.

In comparison with the initial findings, metachronous adenomas are, in general, significantly smaller ones (p < 0.00001), more frequently tubular lesions (p < 0.00001) and bearing less often high-grade dysplasia (p < 0.00001). Adenomas of advanced pathology were significantly less often found during follow-up than at baseline examination (p < 0.0001). These differences are found between the initial and four subsequent generations of metachronous adenomas. Patients with adenomas of advanced pathology at baseline have a significantly higher risk for metachronous adenomas of advanced pathology (RR 1.51; 95%CI 1.04-1.93) at the first recurrence.

Metachronous adenomas show uniform characteristics of being small tubular lesions rarely bearing high-grade dysplasia. Thus, regular surveillance examinations can provide sufficient colorectal carcinoma prevention.