A Case of Unresectable Gastric Cancer with Paraaortic Lymph Node Metastasis Treated with Conversion Therapy

We present a case of advanced gastric cancer with paraaortic lymph node metastasis successfully treated by conversion therapy. The patient was a 71‒year‒old male. Because of paraaortic lymph node metastasis, we initiated intensive chemotherapy with S‒1, oxaliplatin, and trastuzumab. After 6 courses, CT examination revealed that the size of the primary tumor decreased, suggesting a complete response(CR). Furthermore, the metastatic lymph nodes decreased in both number and size, suggesting a partial response(PR). We continued chemotherapy, changing to S‒1 and trastuzumab only because of Grade 3 neutropenia, and conducted continuous infusion chemotherapy. After 5 courses, we performed an upper gastrointestinal endoscopy. The primary tumor recurred, suggesting a progressive disease(PD), while metastasis to the paraaortic lymph nodes disappeared. We decided that a curative resection was possible and performed distal gastrectomy with D2 and paraaortic lymph node dissection. The postoperative courses were uneventful, and the patient was discharged from the hospital 12 days postoperation. The patient is well without any recurrence of cancer at 1 year 3 months postoperation. Conversion therapy may offer the possibility of prolonged survival for patients with gastric cancer previously considered unresectable.