PATIENT CHARACTERISTICS: Age: Not specified Performance Status: ECOG 0-3 Life Expectancy: Not specified Hematopoietic: WBC at least 3,500/mm3 Platelet count at least 150,000/mm3 Hepatic: Bilirubin no greater than 1.5 mg/dL OR 3.0 mg/dL in patients with liver metastases Liver enzymes no greater than 3.0 times upper limit of normal (in patients with liver metastases) Renal: Not specified Other: Not pregnant or lactating Fertile patients must use effective contraception