A Novel Pathology-Based Preoperative Risk Score to Predict Locoregional Residual and Distant Disease and Survival for Incidental Gallbladder Cancer: A 10-Institution Study from the U.S. Extrahepatic Biliary Malignancy Consortium.

BACKGROUND: This study was designed to develop a more robust predictive model, beyond T-stage alone, for incidental gallbladder cancer (IGBC) for discovering locoregional residual (LRD) and distant disease (DD) at reoperation, and estimating overall survival (OS). T-stage alone is currently used to guide treatment for incidental gallbladder cancer. Residual disease at re-resection is the most important factor in predicting outcomes.

METHODS: All patients with IGBC who underwent reoperation at 10 institutions from 2000 to 2015 were included. Routine pathology data from initial cholecystectomy was utilized to create the gallbladder cancer predictive risk score (GBRS).

RESULTS: Of 449 patients with gallbladder cancer, 262 (58 %) were incidentally discovered and underwent reoperation. Advanced T-stage, grade, and presence of lymphovascular (LVI) and perineural (PNI) invasion were all associated with increased rates of DD and LRD and decreased OS. Each pathologic characteristic was assigned a value (T1a: 0, T1b: 1, T2: 2, T3/4: 3; well-diff: 1, mod-diff: 2, poor-diff: 3; LVI-neg: 1, LVI-pos: 2; PNI-neg: 1, PNI-pos: 2), which added to a total GBRS score from 3 to 10. The scores were separated into three risk-groups (low: 3-4, intermediate: 5-7, high: 8-10). Each progressive GBRS group was associated with an increased incidence LRD and DD at the time of re-resection and reduced OS.

CONCLUSIONS: By accounting for subtle pathologic variations within each T-stage, this novel predictive risk-score better stratifies patients with incidentally discovered gallbladder cancer. Compared with T-stage alone, it more accurately identifies patients at risk for locoregional-residual and distant disease and predicts long-term survival as it redistributes T1b, T2, and T3 disease across separate risk-groups based on additional biologic features. This score may help to optimize treatment strategy for patients with incidentally discovered gallbladder cancer.