Gemcitabine and Monoclonal Antibody Therapy in Treating Patients With Metastatic Cancer of the Pancreas

RATIONALE: Drugs used in chemotherapy use different ways to stop tumor cells from dividing so they stop growing or die. Monoclonal antibodies such as trastuzumab can locate tumor cells and either kill them or deliver tumor-killing substances to them without harming normal cells. Combining monoclonal antibody therapy with chemotherapy may kill more tumor cells. PURPOSE: Phase II trial to study the effectiveness of gemcitabine and trastuzumab in treating patients who have metastatic cancer of the pancreas that overexpresses HER2/neu.