Combination Chemotherapy in Treating Patients With Metastatic Cancer of an Unknown Site of Origin

DISEASE CHARACTERISTICS: Histologically confirmed metastatic carcinoma of unknown primary Adenocarcinoma or non-adenocarcinoma No axillary lymph node metastases as sole site of disease in female patients No peritoneal carcinomatosis as sole site of disease in female patients No squamous cell carcinoma in cervical lymph nodes as sole site of disease in male or female patients No neuroendocrine tumors No elevated alpha-fetoprotein, beta-HCG, or PSA PATIENT CHARACTERISTICS: Age: 18 and over Performance status: Karnofsky 60-100% Life expectancy: More than 3 months Hematopoietic: WBC at least 3,000/mm3 Absolute neutrophil count at least 1,500/mm3 Platelet count at least 100,000/mm3 Hemoglobin at least 10 g/dL Hepatic: Bilirubin less than 1.8 mg/dL Renal: Creatinine less than 1.5 times upper limit of normal (ULN) Urea less than 1.5 times ULN Glomerular filtration rate at least 60 mL/min Cardiovascular: LVEF at least 50% by echocardiogram or MUGA scan No uncontrolled angina pectoris No heart failure No clinically significant uncontrolled cardiac arrhythmias No abnormal EKG Other: Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception during and for 1 year after study No other prior malignancy except adequately treated non-melanoma skin cancer or carcinoma in situ of the cervix No medical or psychiatric condition that would preclude study No other serious uncontrolled medical condition PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: No prior chemotherapy for carcinoma of unknown primary Endocrine therapy: Not specified Radiotherapy: Prior radiotherapy allowed except to sole site of measurable or evaluable disease Concurrent palliative radiotherapy allowed except to sole site of measurable or evaluable disease Surgery: Not specified Other: No other concurrent experimental drugs