A method is provided for treating or ameliorating a high-grade glioma in a patient, which method comprises intracerebral administering of a radioactive agent characterized by a short-range cytotoxic ionizing radiation by convection-enhanced delivery. Further, a radioactive agent characterized by a short-range cytotoxic ionizing radiation is provided for use in treating or ameliorating a high-grade glioma, where the agent is administered by intracerebral convection-enhanced delivery