PATIENT CHARACTERISTICS: Age: 18 to 75 Performance status: 0 or 1 Life expectancy: At least 3 months Hematopoietic: WBC at least 3,500/mm3 Platelet count at least 100,000/mm3 Hepatic: Bilirubin no greater than 1.5 times upper limit of normal (ULN) SGOT or SGPT no greater than 2 times ULN (5 times ULN if related to liver metastases) Renal: Creatinine no greater than 1.25 times ULN Cardiovascular: No New York Heart Association class III or IV heart disease No congestive heart failure No symptomatic coronary artery disease No cardiac arrhythmia unless well controlled with medication No myocardial infarction within the past 12 months Neurologic: No peripheral neuropathy of any origin worse than grade 1 No prior or concurrent seizures or CNS disorder requiring treatment Other: Not pregnant Negative pregnancy test Fertile patients must use effective contraception No dysphagia, malabsorption, or intestinal obstruction that could impact the absorption or excretion of study drug No psychiatric disability precluding informed consent or compliance No prior malignancy within the past 5 years except adequately treated carcinoma in situ of the cervix or localized nonmelanomatous skin cancer No other significant medical condition