A Dutch Prediction Tool to Assess the Risk of Incidental Gallbladder Cancers in Cholecystectomies for Benign Gallstone Disease

Introduction: A selective histopathologic (Sel-HP) policy of gallbladder specimens following cholecystectomy is increasingly implemented in low incidence countries. However, the fear of missing incidental gallbladder cancer (iGBC) persists and thereby restrict further implementation of a Sel-HP policy. This study aims to develop a diagnostic prediction model for selecting gallbladders in need of histopathologic examination after cholecystectomy. Method: A registration based retrospective cohort study of nine hospitals in the Southern part of the Netherlands between 2004 and 2014 was used. Five potential clinical predictors for gallbladder cancer (GBC) were selected based on previous literature and expert opinion. The prediction model was internally validated by bootstrapping. Discriminative capacity and accuracy were tested by assessing the area under the receiver operating characteristic curve (AUC) Nagelkerke Pseudo-R2 and Brier score. Finally, a clinical 4-step protocol was formulated using radiological, clinical indications correlated with high susceptibility for GBC, the clinical prediction model and finally the macroscopic examination of the gallbladder. Results: The prediction model was developed using a cohort of 22025 gallbladders containing 75 GBC cases. A model was developed including the following variables: age, sex, urgency, type of surgery and indication for surgery. The AUC was 90.3% (95% confidence interval 86.2% – 94.4%), indicating a good discriminative ability of the model. The calibration plot indicated good calibration of the predicted probabilities. Conclusions: We developed a clinical prediction model for selecting gallbladder specimens for histopathologic examination after cholecystectomy for ruling out GBC. This protocol will support surgeons in selecting appropriate gallbladders specimens for selective pathologic policy.