Conversion therapy of gastric cancer with massive malignant ascites and ovarian metastases by systemic and intraperitoneal chemotherapy.

Intravenous and intraperitoneal paclitaxel with S-1 is showing promising results in gastric cancer with peritoneal metastases. We herein report a successful conversion of unresectable to resectable disease using combination chemotherapy with trastuzumab. The patient was a 39-year-old woman with human epidermal growth factor receptor 2-positive gastric cancer with peritoneal, pulmonary and bilateral ovarian metastases. After 6 cycles of S-1 plus cisplatin with trastuzumab, followed by 15 cycles of intravenous and intraperitoneal paclitaxel with S-1 and trastuzumab, the pulmonary and peritoneal metastases exhibited complete response and no evidence of malignancy was found on diagnostic laparoscopy. We performed metastasectomy of the bilateral sizeable ovaries, followed by total gastrectomy. The patient had no recurrence for 16 months after the gastrectomy. Therefore, satisfactory response to systemic and intraperitoneal chemotherapy may convert unresectable to resectable disease, and primary tumor resection with ovarian metastasectomy may prolong survival. This combination chemotherapy has the potential of becoming a conversion therapy for gastric cancer with peritoneal metastases, even if ascites and ovarian metastases are extensive.