DISEASE CHARACTERISTICS: Histologically confirmed recurrent or refractory solid malignant tumors of childhood including: Soft tissue sarcoma Rhabdomyosarcoma Nonrhabdomyosarcoma Extraosseous Ewing's sarcoma CNS tumors Astrocytoma Primitive neuroectodermal tumor Atypical teratoid/rhabdoid tumors Ependymoma Recurrent neuroblastoma Measurable disease No more than 2 prior treatment regimens