Pathological complete response in a case of HER2-positive gastric cancer with peritoneal dissemination treated with trastuzumab in combination with chemotherapy

Trastuzumab in combination with cisplatin and capecitabine could be a new standard treatment for patients with HER2-positive advanced gastric cancer. We herein report a case of advanced gastric cancer with peritoneal dissemination that was successfully treated with trastuzumab combined with cisplatin and capecitabine followed by gastrectomy. A 49-year-old man complained of epigastric pain and was diagnosed with advanced gastric cancer. A staging laparoscopy revealed peritoneal dissemination that was overexpressing HER2 protein. After five courses of chemotherapy comprising trastuzumab, cisplatin and capecitabine, laparoscopic restaging was performed. The disseminated nodules had disappeared, and biopsy of the scar of peritoneal seeding and cytology of the peritoneal lavage fluid both found no malignant cells. Therefore, total gastrectomy with D2 lymph node dissection was performed. Pathologically, there were no residual tumor cells in the resected stomach or peritoneal wall. Trastuzumab in combination with chemotherapy may have curative potential for peritoneal dissemination from HER2-positive gastric cancer.