Proposal of a new staging system for intrahepatic cholangiocarcinoma: Analysis of surgical patients from a nationwide survey of Liver Cancer Study Group of Japan.

4075 Background: In the current AJCC/UICC staging system 7thed. for intrahepatic cholangiocarcinoma (ICC), tumor size was excluded and “periductal invasion” was added as a new factor determining T-category. However, prognostic significance of tumor size and periductal invasion remains unclear. Methods: Of a total of 1216 patients who underwent surgical resection for ICC between 2000 and 2005 on Japanese nationwide database by Liver Cancer Study Group of Japan (LCSGJ), 756 patients with histologically confirmed mass-forming dominant ICC were studied. A multivariate analysis of the clinicopathological factors on the survivals of patients were performed using the data of 419 patients with complete set of the valid data. A new staging system was customized based on the results of the multivariate analyses. Results: The overall survivals were best stratified with a cut-off value of 2 cm with the minimal p-value to discriminate the survivals of patients. The 5-year survival rate of the 15 patients with ICC < / = 2cm without nodal metastasis or vascular invasion was 100%, suggesting surgical resection offers cure of the disease and these cohort can be defined as T1. Multivariate analysis of prognostic factors for all 419 patients showed that tumor size (HR = 2.487, CI = 0.912-6.780), tumor number (HR = 2.570, CI = 1.814-3.643), nodal metastasis (HR = 2.818, CI = 1.992-3.987) and distant metastasis (HR = 2.940, CI = 1.258-6.869) were independent and significant prognostic factors. The survival curves of N0M0 patients were well-stratified using a new T classification regulated by the 1) tumor size ( < / = 2cm, > 2cm), 2) tumor number and 3) portal vein, arterial or major biliary invasion. The survivals of patients with T1-3N1M0 were as good as those of T4N0M0 patients, and thereby categorized as Stage IVA, discriminating from Stage IVB, a group of T4N1M0 or M1. Conclusions: Tumor size with a cut-off value of 2cm and major biliary invasion were important prognostic factors for survival. The proposed new staging system would be useful for assigning surgical indication for selected patients even with nodal metastasis.