Given that lower OPG expression was significantly correlated with poor RFS in our cohort, and that the liver is the most frequent site of recurrence in CRC, we then compared OPG expression between the primary site and liver metastases obtained from 31 patients with CRC who showed liver metastases and underwent resection at both sites at our institute (Fig. 1D, Supplementary Fig. S2B and Table 2). This evidence concerns the gene TNFRSF11B and colorectal carcinoma.