To Örebro University

AIM: The selective use of defunctioning stomas in anterior resection for rectal cancer hinges on accurately predicting anastomotic leakage. The aim of this study was to develop a prediction model for use in a prospective randomized clinical trial.

METHOD: Colorectal Cancer Database (CRCBaSe) Sweden was used to identify patients who underwent low anterior resection for rectal cancer 2007-2021. Eligibility criteria mirrored the forthcoming SELective defunctioning Stoma Approach in low anterior resection for rectal cancer (SELSA) trial, including patients <80 years of age and with American Society of Anaesthesiologists' (ASA) physical status grade of <III; further, patients without a defunctioning stoma were excluded. The outcome comprised anastomotic leakage within 30 days or in-hospital. Candidate predictors included age, sex, ASA grade, cardiovascular disease, diabetes, body mass index (BMI), tumour stage, tumour height, and neoadjuvant therapy. Seven models were developed and internally validated using bootstrapping. A threshold of a predicted leakage risk of ≤10% was chosen for trial implementation. Validation was conducted using chart-reviewed data from a nested cohort.

RESULTS: Of the 2727 eligible patients, 199 (7.3%) were registered with an anastomotic leakage. All models demonstrated similar performance, with prediction instability observed for risks exceeding 12.5%. The preferred model included three significant predictors: male sex (OR 2.00; 95% CI: 1.45-2.75), BMI >30 kg/m2 (OR 1.82; 95% CI: 1.21-2.74), and radiotherapy (OR 1.90; 95% CI: 1.35-2.69). The bootstrapped area under the curve (AUC) was 0.64 (95% CI: 0.62-0.65), with a negative predictive value of 94.6% (95% CI: 93.7%-95.6%). For the validation cohort, the corresponding estimates were 0.66 (95% CI: 0.59-0.74) and 89.5% (95% CI: 86.2%-92.5%).

CONCLUSION: Accuracy of anastomotic leakage prediction using registry-based data is moderate; however, the model's ability to rule out a >10% risk is considered appropriate for trial use.