Stoma-free Survival After Rectal Cancer Resection With Anastomotic Leakage: Development and Validation of a Prediction Model in a Large International Cohort

Objective: This study aimed to develop and validate a prediction model (STOMA-score) for one-year stoma-free survival in rectal cancer (RC) patients with anastomotic leakage (AL). Background: AL after RC resection often results in a permanent stoma. Methods: This international retrospective cohort study (TENTACLE-Rectum) encompassed 216 participating centres, and included patients who developed AL after RC surgery between 2014-2018. Clinically relevant predictors for one-year stoma-free survival were included in uni- and multivariable logistic regression models. The STOMA-score was developed and internally validated in a cohort of patients operated between 2014-2017, with subsequent temporal validation in a 2018 cohort. The discriminative power and calibration of the models' performance were evaluated. Results: This study included 2499 AL patients; 1954 in the development cohort and 545 in the validation cohort. Baseline characteristics were comparable. One-year stoma-free survival was 45.0% in the development cohort and 43.7% in the validation cohort. The following predictors were included in the STOMA-score: sex, age, ASA-classification, body mass index, clinical M-disease, neoadjuvant therapy, abdominal- and transanal approach, primary defunctioning stoma, multivisceral resection, clinical setting in which AL was diagnosed, postoperative day of AL diagnosis, abdominal contamination, anastomotic defect circumference, bowel wall ischemia, anastomotic fistula, retraction and reactivation leakage. The STOMA-score showed good discrimination and calibration (c-index 0.71, 95%CI 0.66-0.76). Conclusion: The STOMA-score consists of eighteen clinically relevant factors and estimates the individual risk for one-year stoma-free survival in patients with AL after RC surgery, which may improve patient counselling and give guidance when analyzing efficacy of different treatment strategies in future studies.