Background: We wanted to assess the influence of various surveillance intervals on the risk of new neoplasia after removal of pedunculated and small sessile tubular and tubulovillous adenomas.
Methods: After initial colonoscopic polypectomy patients were randomized to surveillance with either 2 years (group A) or 4 years (group B) between colorectal examinations.
Results: The cumulated risk of a patient having new adenomas was 35.0% (28.7-41.4%) in group A and 35.5% (28.4-42.7%) in group B after 48 months. The risk increased to 44.9% (36.0-53.9%) and 60.1% (48.5-71.7%), respectively, after 96 months. The risk of significant neoplasia (carcinoma or adenoma with villous structure, severe dysplasia, or diameter > 10 mm) was 5.2% (2.3-8.1%) and 8.6% (3.8-13.3%) after 48 months and 8.6% (4.2-13.0%) and 17.4% (7.6-27.2%) after 96 months. More than one adenoma at first examination was associated with higher risk of new adenomas. Furthermore, we found a tendency for age above 60 years and male gender to be associated with higher risk of new adenomas. More than two adenomas at first examination was the only factor found to be associated with a higher risk of new significant neoplasia. One patient in group A and two patients in group B developed cancer, which is not significantly different from the number expected (3.43) in the average Danish population (RR = 0.9, 0.2-2.6).
Conclusion: After colonoscopy with removal of all polyps, colorectal examination at 4 years resulted in a similar risk of new adenomas compared with examinations at 2 and 4 years. However, new significant neoplasia tended to be more frequent when first surveillance was at 4 years. Extending the surveillance to 8 years also tended to increase the risk more in the group being examined every 4 years, but reduction of the number of surveillance examinations by more than 50% and a probable reduction of complications from surveillance examinations themselves may justify a recommendation for the longest interval.