The effect of chemotherapy against micrometastases and isolated tumor cells in lymph nodes: an in vivo study.

BACKGROUND The effect of perioperative chemotherapy against micrometastasis has not been elucidated. An in vivo model was established in which a gastric cancer cell line, GCIY-EGFP, metastasizes spontaneously to the lymph nodes when inoculated subcutaneously. MATERIALS AND METHODS After induction of the primary tumor by inoculation of 5 x 10(6) GCIY-EGFP cells into the lower abdominal wall of KSN nude mice, preoperative treatment with S-1 and docetaxel, or postoperative treatment with S-1 was given in addition to resection of the primary tumor to assess the efficacy of chemotherapy on isolated tumor cells (ITC) and micrometastases in the lymph nodes. RESULTS Resection of the primary tumor led to spontaneous regression of ITC but not of micrometastases. Chemotherapy delivered at 3 weeks after the inoculation of tumor cells, whether before or after surgery, was effective against micrometastasis and reduced the risk of recurrence in the lymph nodes, although not as effective against the primary tumor. Once failed to be eradicated, nodal disease grew swiftly after cessation of the chemotherapy. CONCLUSION ITC and micrometastases in the lymph nodes are vulnerable to chemotherapy. When objective response is achieved in a neoadjuvant setting, one may not need fear the risk of systemic disease spread during the course of the treatment.