Complete Response of Locally Advanced Gastric Cancer with Pancreatic Invasion and Gastric Outlet Obstruction after Neoadjuvant Chemotherapy with S-1 and Oxaliplatin

The prognosis of locally advanced gastric cancer is poor even if radical gastrectomy with D2 lymphadenectomy is followed by adjuvant chemotherapy. Hence, neoadjuvant chemotherapy is performed to try to improve the prognosis, as it can significantly downstage the tumor and safely improve the R0 resection rate of patients. Herein, we report a case of locally advanced gastric cancer with pancreatic invasion and gastric outlet obstruction that showed a pathological complete response after neoadjuvant chemotherapy with S-1 and oxaliplatin (SOX). A 74-year-old man presented to our hospital with abdominal pain and pyloric stenosis. CT images revealed a cStage IVb, cT4b tumor in the pancreas, cN1, cM0. Therefore, we performed laparoscopic gastrojejunostomy, and the patient's oral intake improved after surgery; we then administered neoadjuvant chemotherapy with SOX on postoperative day 18, without any surgical complications. After 3 courses of neoadjuvant chemotherapy, the patient underwent radical distal gastrectomy, thereby avoiding pancreatoduodenectomy. Histopathological examination of the resected sample revealed no residual cancer cells, indicating a pathological complete response. No recurrence has occurred for 1 year after surgery. Thus, neoadjuvant chemotherapy with SOX can help in tumor downstaging and may be a multipotent option for the treatment of locally advanced gastric cancer, such as cases with the invasion of other organs; this treatment can result in improved curability and avoid overinvasive surgery.