Long-term survival of HER2 positive gastric cancer patient with multiple liver metastases who obtained pathological complete response after systemic chemotherapy: A case report

INTRODUCTION AND IMPORTANCE: Advanced gastric cancer with liver metastasis is classified as stage IV disease and is generally treated with systemic chemotherapy. Despite recent advances in chemotherapy regimens, the prognosis for gastric cancer with liver metastasis is poor. Recent studies reported the effectiveness of upfront chemotherapy followed by conversion surgery for gastric cancer with liver metastasis. Here, we report a case of an advanced stage IV gastric cancer with liver metastasis treated with upfront systemic chemotherapy followed by conversion surgery, which resulted in pathological complete response and good prognosis. CASE PRESENTATION: A 79-year-old man diagnosed with human epidermal growth factor receptor type 2 (HER2)-positive gastric cancer with multiple liver metastases. He underwent systemic chemotherapy with capecitabine, cisplatin, and trastuzumab. After 14 courses of chemotherapy, the primary tumor and liver metastases shrank, suggesting a partial response. We performed distal gastrectomy with D2 dissection plus lateral hepatic segment resection. Pathological examination revealed no residual tumor cells in the primary or metastatic sites, which indicated a pathological complete response. The postoperative course was uneventful. The patient was discharged on postoperative day 8. Adjuvant S-1 chemotherapy was started on postoperative day 46 and given for 1 year. The patient has been alive and recurrence-free for approximately 5 years after surgery. CONCLUSION: This case shows the possibility of conversion surgery after systemic chemotherapy for stage IV advanced gastric cancer with liver metastasis.