Validation and Modification of the Japanese Classification System for Liver Metastases from Colorectal Cancer: A Multi-institutional Study

Background A Japanese multicenter study disclosed four prognostic indicators of colorectal cancer liver metastases: ≥5 hepatic tumors (HT), HT size > 5 cm, nodal status (N2) of primary cancer, and the presence of extrahepatic metastases (EM). The Japanese classification was then defined as Stage A, HT1 (≤4 lesions and ≤5 cm) and N0/1; Stage B, HT2 (≥5 lesions or >5 cm) and N0/1, or HT1 and N2; and Stage C, HT2 and N2, HT3 (≥5 lesions and >5 cm) with any N, or EM1 (presence of EM) with any HT/N. This study aimed to validate the prognostic reliability in a recent population and to develop a modified staging system that divided Stage C patients. Methods A total of 1185 patients diagnosed with liver metastases between 2007 and 2008 were enrolled in the study. According to the classification, 358, 257, and 570 patients were categorized as Stages A, B, and C, respectively. Stage C was further divided into two groups: Stage C-I, HT3 and N0/1, HT2 and N2, or HT1 and EM1; and Stage C-II, HT3 and N2, or HT2/3 and EM1. Results Cumulative overall survival curves for Stages A, B, and C were significantly different between each two stages ( p