PATIENT CHARACTERISTICS: Age: 18 to 80 Performance status: WHO 0-2 Life expectancy: At least 3 months Hematopoietic: Absolute neutrophil count at least 1,500/mm3 Hepatic: AST and ALT no greater than 3 times upper limit of normal (ULN) Alkaline phosphatase no greater than 5 times ULN Renal: Not specified Other: No bowel obstruction No other significant, uncontrolled underlying medical or psychiatric condition No serious active infection Neurologically stable No other prior malignancy except nonmelanomatous skin cancer or carcinoma in situ of the cervix No psychological, social, familial, or geographical condition that would preclude study Not pregnant or nursing Fertile patients must use effective contraception