Gamma knife radiosurgery of radiation-induced intracranial tumors: local control, outcomes, and complications.

Purpose: To determine local control (LC) and complication rates for patients who underwent radiosurgery for radiation-induced intracranial tumors.

Methods And Materials: Review of a prospectively maintained database (2,714 patients) identified 16 patients (20 tumors) with radiation-induced tumors treated with radiosurgery between 1990 and 2004. Tumor types included typical meningioma (n=17), atypical meningioma (n=2), and schwannoma (n=1). Median patient age at radiosurgery was 47.5 years (range, 27-70 years). The median tumor margin dose was 16 Gy (range, 12-20 Gy). Median follow-up was 40.2 months (range, 10.8-146.2 months). Time-to-event outcomes were calculated with Kaplan-Meier estimates.

Results: Three-year and 5-year LC rates were 100%. Three-year and 5-year overall survival rates were 92% and 80%, respectively. Cause-specific survival rates at 3 and 5 years were 100%. Three patients died: 1 had in-field progression 65.1 months after radiosurgery and later died of the tumor, 1 died of progression of a preexisting brain malignancy, and 1 died of an unrelated cause. One patient had increased seizure activity that correlated with development of edema seen on neuroimaging.

Conclusions: LC, survival, and complication rates in our series are comparable to those in previous reports of radiosurgery for intracranial meningiomas. Also, LC rates with radiosurgery are at least comparable to those of surgical series for radiation-induced meningiomas. Radiosurgery is a safe and effective treatment option for radiation-induced intracranial tumors, most of which are typical meningiomas.