Staging of Peripheral-Type Intrahepatic Cholangiocarcinoma: Appraisal of the New TNM Classification and its Modifications

In the seventh edition, the TNM classification for intrahepatic cholangiocarcinoma (IHC) is separated from that for hepatocellular carcinoma. Because it is the first independent classification for IHC, the validity of the new classification needs to be evaluated. The medical records of 93 patients with peripheral-type IHC who underwent treatment (61 resected and 32 unresectable tumors) were retrospectively reviewed focusing on the new TNM classification for IHC. The 5-year survival rate and the median survival time for the 61 patients with resected tumors were 33.9% and 2.05 years, respectively. The survival of the patients with periductal invasion was similar to that of the patients without. The survival of the patients with metastasis to the gastrohepatic lymph nodes (G-LN) was dismal without any 2-year survivors and similar to that of the patients with unresectable tumors (P = 0.247). On multivariate analysis, histologic differentiation (P = 0.034), multiple tumors (P = 0.014), lymph node metastasis (P < 0.001), and distant metastasis other than lymph node metastasis (P = 0.007) were identified as independent prognostic factors. According to the above results, we modified the new TNM classification as follows: IHC with multiple tumors was classified as pT4 disease; periductal invasion was excluded from determinant of the T-categories; and metastasis to G-LN was treated as distant metastasis. The survival curves based on our modifications were better stratified than those based on the new TNM classification. The TNM classification for IHC included some clinical inconsistencies; therefore, we proposed some modifications of the new TNM classification for IHC and demonstrated that these modifications offer better stratification of the survival data. Further revisions are necessary for its improvement.