Risk Stratification Based on Synchronous Neoplasia and Clinical Physicochemical Characteristics Predicts a Higher Incidence of Metachronous Advanced Neoplasia in Patients Undergoing Colorectal Resection for Colorectal Cancer

Purpose: Patients who undergo primary colorectal cancer (CRC) resection remain at increased risk for metachronous advanced neoplasia (MAN) in the remnant colorectum. This study aimed to investigate the incidence and clinicopathological characteristics predictive of MAN development in the residual colon after surgery. Patients and Methods: We retrospectively reviewed 450 primary CRC cases referred to our hospital during a 4-year period. Univariate and multivariate analyses were performed to identify risk factors for MAN. The cumulative incidence of MAN was evaluated by the Cox proportional hazards model. Results: MAN development was confirmed in 78 of the 450 patients (17.3%). Overall 1-, 2-, 3-, and 5-year cumulative probabilities were 0.9%, 4.8%, 9.8%, and 16.1%, respectively, for MAN. Among the clinical and colonoscopic factors at baseline, the independent factors that were significantly associated with MAN were synchronous neoplasia, carcinoembryonic antigen (CEA) level >= 10.0 ng/mL, and index cancer size >= 50 mm. The cumulative probability of MAN was significantly higher for patients with synchronous advanced neoplasia (SAN) than for those without synchronous neoplasia (P = 0.000). A subgroup analysis of patients based on the CEA level and index cancer size indicated that CEA >= 10 ng/mL and index cancer >= 50 mm resulted in a significantly higher cumulative probability of MAN (P = 0.039). Conclusion: Patients with SAN or high preoperative serum CEA levels and large index cancer are at increased risk for early-onset MAN. More intensive surveillance strategies may be appropriate for these groups. Risk stratification based on synchronous neoplasia and clinical physicochemical characteristics requires further investigations involving modified appropriate postoperative colonoscopic surveillance schedules.