Gastroesophageal cancer is the sixth leading cause of cancer-related death worldwide. The 2 most common histologies are squamous cell carcinoma and adenocarcinoma, which has seen an increase in incidence correlating with an increase in obesity in developed countries. Gastroesophageal adenocarcinoma has a preponderance to metastasize early, making it a highly lethal cancer with a low 5-year survival rate of similar to 15-25%. Therefore, for the majority of patients, treatment focuses on palliation and prolongation of survival. Combination chemotherapy regimens, mostly platinum-based, have only modestly prolonged survival in patients with stage IV disease. Recently, it was discovered that the activation of the HER2 receptor plays an important role in a minority of adenocarcinomas of the distal esophagus and stomach. This introduced the treatment option of trastuzumab (Herceptin), a monoclonal antibody directed at the HER2 receptor, which has demonstrated improvement in overall and progression-free survival as noted in the ToGA trial. Currently, the role of Herceptin therapy beyond first-line therapy and outside of combination regimens is not well established. In this case report we review 2 cases of patients with gastroesophageal cancer, with HER2 overexpression, who achieved a robust response to trastuzumab in combination with chemotherapy and were able to maintain a durable response with maintenance trastuzumab monotherapy. (c) 2017 The Author(s) Published by S. Karger AG, Basel.