Clinical impact of pancreatic invasion in T1-stage distal bile duct cancer and prognostic factors associated with long-term survival: A multicenter study

Background/Purpose: The eighth edition of the AJCC staging system introduced a shift in the staging of distal bile duct cancer (DBC), emphasizing the depth of invasion over adjacent organ invasion. This study aimed to evaluate the clinical impact of pancreatic invasion in pT1-stage DBC and identify prognostic factors for long-term survival. Methods: This multicenter retrospective analysis encompassed DBC patients who underwent pancreaticoduodenectomy between 2009 and 2019 in six Korean tertiary centers, specifically those with final pathology confirming AJCC eighth edition T1 stage and intrapancreatic bile duct tumor origin. Primary endpoints were five-year recurrence-free survival (RFS) and overall survival (OS). Secondary objectives included the identification of prognostic determinants. Results: This study involved 287 patients, comprising 190 without and 97 with pancreatic invasion. Pancreatic invasion did not significantly influence five-year OS and RFS rates (OS: without pancreatic invasion 69.9% vs. with pancreatic invasion 54.1%, p =.25; RFS: 56.3% vs. 55.4%, p =.97). Multivariate analysis highlighted male gender, age, lymphovascular invasion, and N stage as significant OS determinants. Notably, male gender, ampulla of Vater invasion, lymphovascular invasion, and N1 stage were also associated with RFS. Conclusions: In pT1 DBC, pancreatic invasion demonstrates no substantial impact on long-term prognosis, in accordance with the depth-based paradigm of the eighth edition AJCC staging system. The prognostic factors influencing OS were identified as male gender, age, lymphovascular invasion, and nodal metastasis.