[A Case of Histological Response of Grade 3 Achieved by Preoperative Chemotherapy with S-1/Oxaliplatin(SOX)].

Histological response of Grade 3 is relatively rare in gastric cancer patients but has recently been observed occasionally. We report the histological response of Grade 3 achieved by S-1/oxaliplatin(SOX)therapy. A 66-year-old man had suffered from epigastralgia when hungry. After 1 month, he visited the department of gastroenterology of our hospital. Upper gastrointestinal endoscopy revealed a type 3 tumor at the lesser curvature of middle gastric body, and poorly differentiated adenocarcinoma was detected by the biopsy examination. Abdominal/pelvic enhanced CT showed wall thickening of the lower gastric body, enlarged regional lymph nodes and para-aortic lymph nodes(No. 16b1). We diagnosed it with Stage Ⅳ. He received 4 courses of SOX therapy. After chemotherapy, upper gastrointestinal endoscopy revealed a residual tumor, although biopsy showed no cancer cells. Abdominal/pelvic enhanced CT showed significantly reduced lymph nodes despite the thickening of the gastric wall. PET-CT revealed indistinct para-aortic lymph nodes. Distal gastrectomy, D2 dissection without para-aortic lymph nodes dissection, and Billroth Ⅰ reconstruction were performed. Histological findings showed no cancer cells in the main lesion or lymph nodes, with only previous cancer cells suspected. The histological response was Grade 3. SOX therapy might be employed in the future as chemotherapy before conversion surgery for Stage Ⅳ gastric cancer.