Background The present study analyzed biliary tract cancer patients registered from 2008 to 2013 in Japan and evaluated the outcomes of biliary tract cancer. Methods A total of 18,606 patients were registered from 2008 to 2013. Cases were analyzed with regard to patient survival according to contiguous extent of the primary tumor (T), node metastasis, and tumor stage using the 3rd English edition of the Japanese classification of the biliary tract cancers. Results Five-year survival rates were 39.8% for gallbladder cancer, 24.2% for perihilar bile duct cancer, 39.1% for distal bile duct cancer, and 61.3% for ampullary region cancer. Significant differences were observed between newly introduced subdivisions in the new Japanese classification for all tumoral sites except gallbladder cancer. The survival rate in patients with #13a metastasis was significantly higher than in patients with distant lymph node metastasis. Conclusions The new Japanese classification adopted the 7th edition of staging system developed by the Union for International Cancer Control staging system. However, numerous aspects of these classification systems remain unvalidated. The present analysis demonstrated the significance of a proportion of T factor subdivisions and classifications of regional lymph nodes in cases of gallbladder cancer in the new Japanese classification. Highlight Ishihara and colleagues conducted a registry study to determine the outcomes of biliary tract cancer and to validate the new Japanese classification based on the UICC staging system 7th edition. Of particular note, survival rates were significantly higher in patients with #13a metastasis than in those with distant lymph node metastasis.
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