DISEASE CHARACTERISTICS: Histologically or cytologically proven solid malignancy for which no curative therapy exists Glioblastoma eligible if following criteria are met: Stable performance status Stable symptoms At least 4 weeks on stable dose of dexamethasone CNS metastases allowed if no progression or no new edema present Measurable or evaluable disease No acute or chronic leukemia or multiple myeloma No known bone marrow involvement with tumor