PATIENT CHARACTERISTICS: Age: 18 and over Performance status: Karnofsky 70-100% Life expectancy: Not specified Hematopoietic: WBC at least 3,000/mm3 Platelet count at least 100,000/mm3 Hemoglobin at least 9 g/dL Absolute neutrophil count at least 1,500/mm3 Hepatic: Bilirubin no greater than 2.0 mg/dL AST or ALT no greater than 5.0 times upper limit of normal (ULN) Alkaline phosphatase no greater than 5.0 times ULN Renal: Creatinine no greater than 1.5 mg/dL Cardiovascular: No clinically significant active heart disease Other: Fertile patients must use effective contraception No history of retinopathy or macular degeneration No other malignancy within the past 5 years except basal cell or squamous cell skin cancer or carcinoma in situ of the cervix No other significant medical and/or psychiatric condition that would preclude study