PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: At least 4 weeks since prior chemotherapy (6 weeks since prior nitrosoureas or mitomycin) and recovered No concurrent cytotoxic therapy Endocrine therapy: Not specified Radiotherapy: At least 4 weeks since prior radiotherapy Surgery: No prior gastrointestinal surgery that would interfere with carbendazim absorption Other: No concurrent use of phenytoin, phenobarbital, valproic acid, or other antiepileptic prophylaxis No concurrent scheduled antacids, such as H2 blockers (e.g., cimetidine or ranitidine) or hydrogen pump inhibitors (e.g., omeprazole), or cisapride