Differences in Chemosensitivity between Primary and Metastatic Tumors in Colorectal Cancer

PURPOSE: We retrospectively evaluated the in vitro chemosensitivity of primary site and metastatic site tumors in colorectal cancer. METHODS: Various resected tumor samples (33 from lymph nodes, 42 from liver, six from lung, and 68 primary tumors) were assessed via a collagen gel droplet-embedded culture drug sensitivity test to determine chemosensitivity to a single agent or a combination of agents. RESULTS: Sensitivity to combination chemotherapy was significantly higher than that of monotherapy in the primary site group, lymph node group, and liver group. There was significant difference between chemosensitivity of primary site and that of liver metastasis in each agent (5-FU, p<0.001; SN38, p = 0.045; 5-FU/SN38, p<0.001; OHP, p = 0.037; 5-FU/OHP, p = 0.045). CONCLUSIONS: Tumors showed greater in vitro chemosensitivity to combination therapy when compared with monotherapy. Further, tumors that had metastasized to the liver were more resistant to chemotherapy when compared with matched primary tumors.