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Abstract
Objective. Because of the high recurrence rates of colorectal adenomas, regular surveillance by colonoscopy has been recommended, but there is still a dearth of information on the long-term results of follow-up colonoscopy after polypectomy. The aims of this study were to determine the differences between initial adenomas and metachronous lesions, to evaluate the effect of long-term surveillance and to describe the hypothetical origin of the colorectal adenoma–carcinoma sequence. Material and methods. Between 1978 and 2003 a total of 1091 patients undergoing periodic surveillance examinations were prospectively documented at the Erlangen Registry of Colorectal Polyps. Differences between initial and metachronous lesions found during long-term follow-up were studied. Statistical analysis using χ2 testing of adenoma characteristics found in four subsequent recurrence periods was carried out, and the relative risk (RR) for the development of metachronous adenomas of advanced pathology was calculated. Results. In comparison with the initial findings, metachronous adenomas are generally significantly smaller lesions (p<0.00001), usually tubular in shape (p<0.00001) and bearing high-grade dysplasia less often (p<0.00001) and are usually located in the right colon (p<0.00001). These differences are found between the initial and four subsequent generations of metachronous adenomas. The number of synchronous adenomas is reduced only in the first recurrence (p<0.001); in the further generations equal proportions of multiplicity are found, as in the baseline examination. Patients with adenomas of advanced pathology, i.e. large, tubulovillous or villous adenomas at baseline, have a significantly higher risk for large (RR 2.73; 95% CI 1.77–4.20), tubulovillous or villous (RR 1.55; 95% CI 1.06–2.25) or multiple (RR 2.45; 95% CI 1.83–3.29) metachronous adenomas at the first recurrence. Conclusions. Metachronous adenomas show the uniform characteristics of being small tubular lesions rarely bearing high-grade dysplasia, usually located in the right colon. Thus regular follow-up colonoscopy can provide sufficient colorectal carcinoma prevention.