Histological evaluation of tumor response in metastatic lymph node after preoperative chemotherapy for gastric cancer

51 Background: Preoperative chemotherapy is thought to be an option for treatment of advanced gastric cancer. However, optimal predictive marker for survival of preoperative chemotherapy had not yet been established. Histological response is thought to be a good candidate of predictive marker, however, it had been determined only in primary tumor, not in the metastatic lymph node. The aim of this study is to evaluate the role of histological response in metastatic lymph node on the survival in patients received preoperative chemotherapy for advanced gastric cancer. Methods: A total of 38 patients who underwent curative resection after preoperative chemotherapy from were included. For histological evaluation in lymph node, we determined it as positive if remaining viable tumor cells are less than 30% of the tumor area at one or more of the resected metastatic lymph nodes. We also evaluated histological response in primary tumor according to the Japanese Gastric Cancer Classification. Results: 21 patients received preoperative chemotherapy as planned neo-adjuvant chemotherapy and remaining 17 received chemotherapy as palliative intent and then converted to surgery. Pathological TNM stage was 0 in 2, I in 5, II in 13, III in 11, and IV in 7, respectively. In lymph node, histological response was able to evaluate in 31 of 38 patients. Among them, positive response was observed in 15 patients. Histological tumor response in primary tumor was grade 0 in 2, grade 1a in 10, grade 1b in 7, grade 2 in 10, and grade 3 in 2. The 3-year relapse-free survival (RFS) rate was significantly better in patients with positive histological response in lymph node (71 %) than in those without response (21 %) (p = 0.003). Similarly, 3-year RFS rate was significantly better in patients with histological response in primary tumor (grade 2, 3) (73 %) than in those without response (grade 0, 1a, 1b) (30 %) (p=0.007). Three-year RFS in patients who demonstrate histological response both in primary tumor and lymph node was as high as 89 %. Conclusions: Histological responses in lymph nodes, as well as primary tumor, appear to be a useful predictive marker for survival in patients underwent curative resection after preoperative chemotherapy.