Unresectable gliomas in children: tumor-volume response to radiation therapy.

Serial tumor volume measurements were performed on computed tomographic (CT) scans or magnetic resonance (MR) images of 12 children treated with radiation therapy for high-grade (three children) or low-grade (nine children) astrocytomas of the optic nerve, thalamus, hypothalamus, cerebellar-pontine angle, and pons. Three types of initial tumor response were observed: Tumor volume increased in four children, remained unchanged in one, and decreased immediately after completion of radiation therapy in the others. High-grade tumors regressed maximally within 6 months and low-grade tumors within 10-25 months. All high-grade tumors recurred within 12 months. Three low-grade tumors recurred 3, 6 1/2, and 10 years after diagnosis, respectively. The tumor-volume halving time was 60-78 days for high-grade tumors and 108-330 days for low-grade tumors. The tumor doubling time was 48-60 days for high-grade tumors. The posttreatment increase in tumor volume has implications for radiation treatment planning. It did not indicate a poor prognosis.