DISEASE CHARACTERISTICS: Histologically or cytologically confirmed locally advanced or metastatic cancer that is considered incurable and for which no standard curative therapy exists No primary CNS malignancies Measurable evidence of residual, recurrent, or metastatic disease No prior CNS metastases with residual abnormal findings on neuroradiologic studies Prior CNS metastases allowed provided at least 6 months from definitive therapy and a normal CT or MRI of the brain