What is the risk factor for metachronous colorectal carcinoma?

The purpose of this study was to determine the risk factors for developing metachronous colorectal carcinoma and to determine an adequate postoperative colonoscopic surveillance.

Two hundred eighty-four patients, examined by routine colonoscopy after resection for colorectal carcinoma, were reviewed. Clinical and pathologic factors were assessed by multiple logistic regression analysis.

One hundred eighty-three patients with synchronous adenoma or carcinoma at the initial operation had a significantly higher incidence of both metachronous adenoma and carcinoma than the 101 patients without a synchronous lesion. Other clinical factors including age, gender, tumor stage, tumor site, and tumor grade were not significant for an increased incidence of metachronous carcinoma. The presence of synchronous lesions proved to be the only risk factor (relative risk, 3.293; P = 0.0155) for developing metachronous carcinoma. Metachronous carcinoma was detected in 30 patients (10.6 percent) and completely removed from all patients. Mucosal carcinoma was found in 25 patients (8.8 percent) and invasive carcinoma in 5 patients (1.8 percent). All five invasive carcinomas were detected in asymptomatic patients having synchronous lesion. Four patients required a second operation for metachronous carcinoma more than 13 months following the first.

The risk factor for developing metachronous carcinoma is the presence of synchronous adenoma or carcinoma at the initial operation. To detect metachronous carcinoma at a curable stage, annual colonoscopic surveillance should be performed for high-risk patients.