Linac radiosurgery for high-grade gliomas: the University of Florida experience

Stereotactic radiosurgery has been reported as a promising boost technique for the treatment of selected patients with high-grade glioma. The first 11 patients given this treatment at the University of Florida are reported.

Six patients with glioblastoma multiforme and five with anaplastic astrocytoma were carefully selected for treatment with linac radiosurgery. All patients had a Karnofsky performance status > or = 90%. Median age of patients was 42.1 years. External-beam radiotherapy delivered a median dose of 60 Gy. Stereotactic radiosurgery was delivered to the enhancing tumor volume without margin. Median treatment volume was 14 cm3 (equivalent sphere diameter, 3 cm). The maximum volume of any tumor treated was 22.5 cm3 (equivalent sphere diameter, 3.5 cm). Median stereotactic radiosurgery boost dose was 12.5 Gy, and median prescription sphere was the 80% isodose shell.

Despite rigorous selection and aggressive stereotactic boost irradiation, this patient cohort had a median actuarial survival of 17 months. All patients have had progression of intracranial disease within 1 year of radiosurgery, and only 3 of 11 remain alive with a median follow-up of 13 months.

These results differ significantly from others reported. Comparative analysis suggests tumor volume may be an important prognostic factor in patients treated with stereotactic radiosurgery. Future studies need to define appropriate patient cohorts for the boost technique.