A Composite Endpoint of Liver Surgery (CELS): Development and Validation of a Clinically Relevant Endpoint Requiring a Smaller Sample Size

Background. The feasibility of trials in liver surgery using a single-component clinical endpoint is low because single endpoints require large samples due to their low incidence. The current study sought to develop and validate a novel composite endpoint of liver surgery (CELS) to facilitate the generation of more feasible and robust high-level evidence in the field of liver surgery. Methods. Patients who underwent curative-intent hepatectomy for hepatocellular carcinoma, intrahepatic cholangiocarcinoma, or colorectal liver metastasis were identified using a multi-institutional database. Components of CELS were selected based on perioperative liver surgery-specific complications using univariable logistic regression models. The association of CELS with prolonged length of stay (LOS) and surgery-related death was evaluated and externally validated. Sample sizes were calculated for both individual outcomes and CELS. Results. Among 1958 patients, 377 (19.3%) met CELS criteria based on postoperative bile leak (n = 221, 11.3%), post-hepatectomy liver failure (n = 71, 3.6%), post-hepatectomy hemorrhage (n = 38, 1.9%), or intraoperative blood loss of 2000 ml or greater (n = 101, 5.2%). CELS demonstrated favorable discriminative accuracy of surgery-related death (analytic cohort: area under the curve [AUC], 0.79 vs external validation cohort: AUC, 0.85). In addition LOS was longer among the patients with a positive CELS (analytic cohort: 14 vs. 9 days [p < 0.001] vs. the validation cohort: 10 vs. 6 days [p < 0.001]). Relative to individual endpoints, CELS allowed a 45.8-91.6% reduction in sample size. Conclusion. CELS effectively predicted surgery-related death and can be used as a standardized, clinically relevant endpoint in prospective trials, facilitating smaller sample sizes and enhancing feasibility compared with single quality outcome metrics.