Successful conversion surgery for unresectable gastric cancer with giant para-aortic lymph node metastasis after downsizing chemotherapy with S-1 and oxaliplatin: a case report

BACKGROUND: Although patients with stage IV gastric cancer who respond well to systemic chemotherapy can be treated with gastrectomy, the prognosis of patients with unresectable gastric cancer with para-aortic lymph node metastasis is poor. We herein report a case of remnant gastric cancer with para-aortic lymph node metastasis that was treated with potentially curative conversion surgery after showing a complete response to chemotherapy with S-1 and oxaliplatin (SOX). CASE PRESENTATION: An 81-year-old man was diagnosed with type 3 remnant gastric cancer with giant para-aortic lymph node metastasis, and he received SOX chemotherapy. After three courses of SOX chemotherapy, the primary tumor and para-aortic lymph node metastases markedly reduced in size, indicating a partial response. Because conversion surgery was possible, the patient underwent total remnant gastrectomy with D2 and para-aortic lymph node dissection. Histological examination revealed no residual cancer cells in the resected stomach and lymph nodes. The patient was diagnosed with a complete pathological response and was discharged on postoperative day 24. Currently, 1 year after surgery, the patient is alive and has not shown any tumor recurrence. CONCLUSION: To the best of our knowledge, this is the first case of advanced remnant gastric cancer with giant para-aortic lymph node metastasis that showed a pathological complete response and favorable outcome after SOX chemotherapy.