The incidence of colorectal neoplasia in acromegaly
PA Kelly1, PD Fairclough2, JP Monson1, AB Grossman1, SL Chew1, GM Besser1 & PJ Jenkins1
Background: Patients with acromegaly have an increased risk of colorectal neoplasia. In non-acromegalic subjects, carcinomas develop from dysplastic tubular adenomas and colonoscopic removal of these reduces the subsequent incidence of carcinoma. The frequency of such screening in acromegaly is controversial and it is uncertain which patients should be considered to be at particular increased risk. Methods: We reviewed the incidence of new colonic lesions amongst our large cohort of over 350 acromegalic patients in our colonoscopic surveillance program. To date, 102 patients have had a second colonoscopy, at a median age of 58.1 years (range 39.5 to 77.0), and a median interval of 43 months (range 4 to 87) after the original colonoscopy when all visible lesions were removed. 32 had prior dysplastic adenomas and 38 patients had elevated serum IGF-1 levels. Results: New dysplastic adenomas were found in 14 patients (13.7%), 8 proximal to the splenic flexure. A prior adenoma, being present in 7, did not confer an increased risk of developing new adenomas (p=0.2). Hyperplastic polyps were found in 25. The median IGF-1 level was significantly higher in those patients with a new adenoma, compared to those with either a hyperplastic polyp or normal colon (median plus/minus SEM: 337 plus/minus 40 v. 231 plus/minus 26 (p<0.03) v. 22 plus/minus 15 (p<0.005) nannograms per millilitre respectively). The relative risk of developing a new adenoma in patients with a raised serum IGF-1 level was 8.3 (95% CI 1.9 to 48.8, p<0.002). Conclusions: Elevated serum IGF-1 confers an increased risk of colorectal neoplasia in acromegaly. We suggest that these patients should be examined at 3 yearly intervals. Prior disease may influence the future risk of an adenoma less than previously thought. These observations support the aggressive lowering of serum IGF-1 levels in acromegaly.