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

DISEASE CHARACTERISTICS: Histologically proven metastatic pancreatic cancer with overexpression of HER2/neu Patients in whom there is inadequate tissue to evaluate for HER2/neu overexpression but who have elevated serum HER2/neu antigen levels are eligible Radiographically measurable disease May have metastatic disease in which primary lesion is measurable but metastatic lesions are not measurable Ascites is not measurable PATIENT CHARACTERISTICS: Age: Over 18 Performance status: ECOG 0-2 Life expectancy: Not specified Hematopoietic: Granulocyte count at least 1,500/mm3 Platelet count at least 100,000/mm3 Hepatic: Bilirubin no greater than 3.0 mg/dL Greater than 3 times normal if increase in bilirubin is due to biliary obstruction from tumor as long as biliary system is stented or bypassed and bilirubin, SGOT, or SGPT is stable or decreasing SGOT no greater than 3 times normal No greater than 5 times normal if liver metastases present OR Greater than 5 times normal if increase in SGOT or SGPT is due to biliary obstruction from tumor as long as biliary system is stented or bypassed and biliary SGOT or SGPT is stable or decreasing Renal: Creatinine no greater than 2.0 mg/dL Cardiovascular: No unstable angina No prior congestive heart failure No prior myocardial infarction LVEF at least 45% by MUGA or echocardiogram Other: Not pregnant Fertile patients must use effective contraception PRIOR CONCURRENT THERAPY: Biologic therapy: No prior trastuzumab No concurrent growth factors Chemotherapy: No prior anthracyclines No prior gemcitabine except prior low dose (no greater than 300 mg/m2/week) gemcitabine with radiotherapy At least 6 months since prior adjuvant therapy More than 2 weeks since other prior chemotherapy No other concurrent cytotoxic chemotherapy Endocrine therapy: Not specified Radiotherapy: See Chemotherapy More than 2 weeks since prior radiotherapy No concurrent radiotherapy Surgery: Not specified Other: No other concurrent investigational agents