Characteristics and risk factors of synchronous and metachronous polyp in colorectal cancer

BACKGROUND/AIMS: Detection and removal of adenomatous polyps with colonoscopy is known to be the best preventive method for the colon cancer. With removal of synchronous colon polyps, the risk of metachronous cancer seems to be decreased effectively. However, the preoperative evaluation of entire colon is frequently impossible due to luminal obstructive lesion. Therefore, it is important to evaluate entire colon in postoperative period as earlier as possible. The aim of current study is to analyze the characteristics and risk factors of synchronous as well as metachronous polyps. METHODS: From Jan. 1998 to Dec. 2001, among the patients who received operative treatment for colon cancer in Yonsei University, Severance Hospital, 972 patients, who had underwent preoperative endoscopic evaluation and surveillance above one year after operation, were enrolled. RESULTS: In 617 patients who had completed total colonic evaluation within one year after operation, 45.93% of cases had synchronous polyps, 17.0% advanced polyps, and 5.8% synchronous cancer. The incidence of synchronous and advanced synchronous polyps was high in elderly (>or=60 year), male patients (p<0.05). In 166 patients who had underwent postoperative colonoscopy after one year, 25.3% had metachronous polyps, 3.0% advanced polyps, and 0.6% metachronous cancer. The presence of synchronous polyps was associated with the risk of metachronous polyps (p<0.05). CONCLUSIONS: Complete colonic evaluation during perioperative period should be recommended to identify precancerous lesions, which can contribute to reduce the development of colon cancer.