Adenoma incidence after resection of sporadic colorectal cancer with microsatellite instability

Background and Objectives Microsatellite instability (MSI) tumors that develop via the mismatch repair (MMR) gene pathway show rapid growth. It is unknown if patients with sporadic colorectal cancer (CRC) with MSI would benefit from a shorter interval between colonoscopies. The purpose of this study is to determine if there is a difference in adenoma incidence based on the presence of MSI in patients with sporadic CRC. Methods We retrospectively reviewed the incidence of a recurring adenoma at the 1‐ and 3‐year surveillance colonoscopies in 426 patients who had sporadic CRC after surgery Results The number of high MSI (MSI‐H), low MSI (MSI‐L), and microsatellite stable (MSS) tumors were 38 (9%), 27 (6%), and 361 (85%), respectively. After 1 year, the incidence of adenoma (13% vs. 16% for MSI‐L + MSS vs. MSI‐H, P = 0.61) or advanced adenoma (3% vs. 8% for MSI‐L + MSS vs. MSI‐H, P = 0.14) did not differ based on MSI status. The incidence of adenoma or advanced adenoma also did not differ based on MSI status at the 3‐year surveillance colonoscopy. Conclusions Our study does not show recommendations for a shorter interval for subsequent colonoscopies in patients with sporadic CRC with MSI‐H. Further studies on a large scale are needed. J. Surg. Oncol. 2010; 101:577–581. © 2010 Wiley‐Liss, Inc.