Proposal of a novel H category-based classification of colorectal liver metastases based on a Japanese nationwide survey.

Abstract

The conventional H category-based classification for colorectal liver metastases (CRLM) was created by equal weighting of tumor number and tumor size; however, our previous nomogram to predict postoperative disease-free survival demonstrated that CRLM ≥5 as a parameter provided 4.5 times greater impact compared with a largest CRLM size >5cm. A total of 3815 patients newly diagnosed with CRLM between 2005 and 2007, including 2220 resectable cases, were investigated. Six groups were created based on largest lesion size (≤ 5 vs >5cm) and lesion number (1, 2-4, and ≥5). The novel (n) H1, nH2, and nH3 categories were defined as solitary lesions with a size ≤5cm; lesions other than nH1 or nH3; and ≥5 lesions with any lesion size, respectively. In the resectable cohort, the 5-year cumulative overall survival rates were 64.0%, 53.5%, and 42.6% in the nH1, nH2, and nH3 groups, respectively (P<.001), and no significant differences were observed between the conventional H2 and H3 categories. In the overall cohort, the discrimination ability of the two classifications were comparable. The novel H category-based classification might be beneficial in predicting overall survival in patients with CRLM independent of their resectability.