Pancreatic and Duodenal Invasion in Distal Bile Duct Cancer: Paradox in the Tumor Classification of the American Joint Committee on Cancer

BACKGROUND: Distal bile duct cancer often invades the pancreas and/or duodenum. Invasion of the pancreas is defined as a T3 and that of the duodenum as a T4 tumor in the T classification of the American Joint Committee on Cancer (AJCC). The aim of this study was to assess whether this T classification is rational from the viewpoint of prognostic power. METHOD: Ninety-five patients with distal bile duct cancer were retrospectively analyzed according to the current T classification of the AJCC. RESULTS: The main determinant of pT3 (n = 32) and pT4 (n = 30) was pancreatic and duodenal invasion, respectively, and the survival rates for patients with pT3 and pT4 are similar (p = 0.595). Duodenal invasion was present in 39% of the patients with pancreatic invasion, whereas pancreatic invasion was observed in 86% of those with duodenal invasion. The survival for patients with pancreatic invasion was not significantly different (p = 0.283) whether or not there was concomitant duodenal invasion (n = 19 and n = 37, respectively). Multivariate analysis identified venous invasion, distant metastasis, histologic grade, and pancreatic invasion as independent prognostic factors. CONCLUSION: Although duodenal invasion usually occurs after pancreatic invasion, it is not a significant prognostic factor while pancreatic invasion is. The current T classification should be revised since it expresses tumor extension but does not reflect a survival in distal bile duct cancer.