Brainstem Metastases Treated with Stereotactic Radiosurgery: Masked versus Framed Immobilization

-BACKGROUND: Patients with brainstem metastases (BSMs) have minimal surgical options due to high-risk anatomy. To review our efficacy treating BSM using Gamma Knife stereotactic radiosurgery (SRS), we compared results on the basis of the utilization of mask-fixation (MF) or frame-fixation (FF). -METHODS: Data were retrospectively collected for 32 patients. Follow-up data for 49 lesions were analyzed for local control rate (LCR) and objective response rate (ORR). -RESULTS: Primary cancers included lung, breast, and melanoma; most lesions were pontine. MF was used in 18 patients. Average tumor volume was 0.99 cm3 (0.005-13.3 cm3). Thirty-nine lesions were treated with single-fraction 16 Gy. Ten lesions were treated in 3-5 fractions with mean dose of 22.5 Gy. Mean follow-up was 14.2 months (1.2-48.2 months). One-year LCR was 94.7%. ORR at last follow-up did not differ between MF and FF (P = 0.81). Average reduction of lesion volume at 6 and 12 months did not differ between MF and FF (64% vs. 45%, P = 0.77; 70% vs. 77%, P = 0.78). Failure occurred in a pontine colorectal cancer metastasis mask-immobilized for treatment with 14 Gy. -CONCLUSIONS: SRS for BSM achieved high LCR despite variability in tumor size and histology with no significant difference between MF and FF. Although trials have his-torically excluded patients with BSM, our data support SRS as a safe and efficacious treatment. This is the first study showing that MF provides equivalent, successful outcomes when compared with FF for patients with BSM.