RATIONALE: Drugs used in chemotherapy, such as gemcitabine hydrochloride, work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. Monoclonal antibodies, such as bevacizumab, can block tumor growth in different ways. Some block the ability of tumor cells to grow and spread. Others find tumor cells an help kill them or carry tumor-killing substances to them. Bevacizumab may also stop the growth of pancreatic cancer by blocking blood flow to the tumor. Giving gemcitabine hydrochloride together with bevacizumab after surgery may kill any remaining tumor cells.