Histologic classification and grading enhances gallbladder cancer staging: A population-based prognostic score validated by the U.S. Extrahepatic Biliary Malignancy Consortium.

Abstract

356 Background: Beyond the most common adenocarcinoma type, several gallbladder cancer (GBC) histologies have been described as being associated with more favorable (papillary) or less favorable outcome (adenosquamous, mucinous, signet ring). We sought to examine the added value of histologic type and grade on the existing AJCC staging system for resected GBC. Methods: Patients who underwent resection of GBC from 1988-2013 were identified using the Surveillance Epidemiology End Results (SEER) registry. A prognostic score was created by assigning points for T stage, N stage, grade and histology based on the regression coefficient in multivariate analysis. The score was externally validated using the US Extrahepatic Biliary Malignancy Consortium (USEBMC) database (2000-2015) and compared with the AJCC staging system. Results: Of 7,915 patients identified in SEER, 83% had adenocarcinoma, 7% papillary, 4% adenosquamous, 4% mucinous, and 2% signet ring. In the USEBMC database, the frequencies of the respective histologies were 86, 9, 2, 1 and 2%. Median survival per histologic type, for SEER and USEBMC respectively, were 45 and 110 mos for papillary, 16 and 24 mos for adenocarcinoma, 14 and 12mos for mucinous, 8 and 4mos for adenosquamous, and 9 and 15mos for signet ring (P between histologies < 0.001 for both cohorts). On multivariate analysis, T stage, N stage, grade and histology were independent predictors of survival. The developed prognostic score, based on points for each of these 4 variables, showed excellent discriminatory ability both in the SEER and USEBMC cohorts. The AUC for the prognostic score was significantly improved compared with the AJCC system (0.69 vs. 0.64,both P < 0.001 using SEER, and 0.76 vs. 0.66,both P < 0.001 using USEBMC). Conclusions: The incorporation of histology and grade into the TNM system allows for a simple and accurate tool to determine prognosis following resection of GBC. [Table: see text]