Radiotherapy for Cerebellar Astrocytomas

Abstract

The majority of cerebellar astrocytomas occurring in children are low grade, and as such there is a limited role for radiotherapy, even if complete resection has not been achieved. Low-grade tumors may also spontaneously regress. Radiotherapy has a place in the treatment of high-grade astrocytomas and where low-grade tumors have progressed despite chemotherapy. Chemotherapy and observation are used to delay the need for radiotherapy, and as the long-term effects are more severe, the younger the child at treatment. Low-grade cerebellar astrocytomas are treated with 54 Gy to the tumor with 1 cm margins on the gross tumor volume. High-grade tumors however should receive 59.4 Gy to a 2 cm margin. Long-term effects of radiotherapy depend on the total dose, the age at treatment, and the irradiated volumes of the organs at risk. Neurocognitive complications of brain tumor treatments are aggravated by the number of surgical complications, the degree of hydrocephalus, the radiation dose, and the volume of the supratentorial brain receiving treatment. New modalities, careful planning, and smaller volumes may ameliorate some of these effects. Long-term follow-up of patients who have undergone radiotherapy needs to be lifelong and should follow cooperative group guidelines.