Hypofractionated Stereotactic Radiation Therapy For Brain Metastases

Stereotactic radiosurgery (SRS) is frequently used in the management of brain metastases, but concerns over potential radionecrosis may limit applications for larger lesions or those in eloquent areas. Hypofractionated stereotactic radiation therapy (HSRT) is often substituted for SRS in these cases. We retrospectively analyzed the outcomes of patients who had received HSRT at our institution, to determine whether the efficacy and toxicity of HSRT are comparable to published data for SRS. All patients treated with HSRT for brain metastases from June 2008 - June 2012 were identified, 70 of whom had follow-up data and were eligible for analysis. Patients who had received prior surgery or SRS to the lesion of interest were excluded. Median tumor size (maximal diameter) was 1.7 cm. The rates of local and distant intracranial failure from the end of treatment, acute toxicity, and the rate of radionecrosis were determined. Overall survival, local control, and distant control were calculated using the Kaplan-Meier method. The prescribed HSRT dose was 25 Gy in 5 fractions (n = 61) or 30 Gy in 10 fractions (n = 5), among 94% of patients. Median overall survival in the cohort was 10.7 months. With a median follow-up time for survivors of 13.5 months, the median time to local progression was 17 months, with a local control rate of 68% at six months and 56% at one year. Acute toxicity was seen in 11 patients (16%), mostly grade 1 (n = 6) or 2 (n = 3), with 2 patients experiencing seizures in the month following the procedure (grade 3). Radiation-induced treatment change was seen on follow-up MRIs in 6 patients (9%). Overall, the outcomes of patients who received HSRT are comparable to those reported for SRS. HSRT appears to be a safe and effective technique to deliver highly focused radiation for patients with brain metastases who would otherwise be ineligible or less suitable to receive SRS.