PRIOR CONCURRENT THERAPY: Biologic therapy: No concurrent immunotherapy Chemotherapy: See Disease Characteristics At least 4 weeks since prior chemotherapy (6 weeks since carboplatin, mitomycin, or nitrosoureas) and recovered No prior SR-45023A No other concurrent chemotherapy Endocrine therapy: No concurrent steroid therapy for brain disease No concurrent hormonal cancer therapy (except contraception, hormone replacement therapy, or corticosteroids) Radiotherapy: See Disease Characteristics At least 4 weeks since prior radiotherapy and recovered No concurrent radiotherapy (except symptomatic radiotherapy for pathologic fractures) Surgery: At least 4 weeks since prior surgery and recovered Other: At least 4 weeks since prior investigational agents No other concurrent investigational agents No concurrent anticoagulation therapy (e.g., heparin) except low dose warfarin for central venous catheter patency No concurrent digoxin, beta blockers, or calcium channel blockers No concurrent H2 histamine inhibitors (e.g., ranitidine, famotidine, or cimetidine), proton pump inhibitors (e.g., omeprazole or lansoprazole), or other drugs that might interfere with study drug absorption