DISEASE CHARACTERISTICS: Histologically or cytologically confirmed nonhematologic malignancy unresponsive to existing therapy or for which no curative therapy exists Patients with prostate cancer must have withdrawn from antiandrogen therapy (flutamide, bicalutamide) for at least 4 weeks and must have progressive disease Measurable or evaluable disease No active brain metastases (e.g., cerebral edema, progression from prior imaging study, requirement for steroids, or clinical symptoms)