Associations of Postoperative Complications Assessed by Clavien-Dindo Classification and Comprehensive Complication Index with Long-Term Overall Survival in Elderly Patients after Radical CRC Resection

Background: Advancing age is associated with high incidence of colorectal cancer (CRC) and high rates of postoperative complications (POCs). However, the impact of of POC severity - evaluated by Clavien-Dindo classification (CDC) or comprehensive complication index (CCI) - on long-term overall survival (OS) in elderly patients after radical CRC resection is not clear. Methods: Elderly patients aged 65 years or more with CRC undergoing radical resection were retrospectively recruited. POC details were collected and evaluated using CDC grades and the CCI, blinded to patients' other information. Risk factors for CDC grade >= II POCs were analyzed by multivariate logistic regression. Effects of CDC grade II-IV POCs on long-term OS were analyzed via propensity-score matching (PSM) analysis followed by Kaplan-Meier curve plotting and multivariate Cox proportional-hazard regression adjusted for all potential confounders. The prognostic value of the CCI was also explored and compared with CDC grades. Results: A total of 614 elderly patients were identified, of which 20, 106, 25, 11, and 13 cases experienced CDC grade I, II, III, IV, and V POCs, respectively. Higher age, female sex, coronary heart diseases, family history of tumors, preoperative anemia, high amount of bleeding during operation, and high positive dissected lymph-node ratio were found to be risk factors for CDC grade II-V POCs. After PSM analyses, CDC grade II-IV POCs were identified to be associated with poor long-term OS, which was also verified in the entire cohort. The CCI was also found to be significantly associated with decreased long-term OS and showed prognostic values similar to CDC grades. Conclusion: Both CDC grades and the CCI can be used to evaluate POCs and are associated with long-term OS in elderly patients undergoing radical CRC resection.