Linac-Based Fractionated Stereotactic Radiotherapy with a Micro-Multileaf Collimator for Brainstem Metastasis

BACKGROUND: To assess the neuroimaging and clinical outcomes in patients with brainstem metastasis (BSM) treated with linac-based fractionated stereotactic radiotherapy (fSRT) with a micro-multileaf collimator. METHODS: Between May 2007 and January 2017, 24 patients (15 male and 9 female) with BSM (25 lesions: midbrain, 10; pons, 13; and medulla oblongata, 2) were consecutively treated with linac-based fSRT. BSM originated from the lung (n = 18, 75.0%), colon (n = 3, 12.5%), and breast (n = 3, 12.5%). The median patient age was 67.0 (range: 42-80) years. Recursive partition analysis classified 2 patients as class I, 17 as class II, and 5 as class III. Overall survival was calculated using the Kaplan-Meier method. RESULTS: Tumor volume ranged from 0.01 to 7.49 cm(3) (median: 0.233 cm(3)), and patients were treated with a dose of 24-40 Gy in 7-13 fractions. The median OS was 9 months after fSRT (95% confidence interval 4.104-13.896). Large tumor volume, presence of brainstem-related symptoms, poor pretreatment Karnofsky performance status, and recursive partition analysis class III were significantly associated with low overall survival. Tumor volume decreased in 18 metastatic lesions, remained stable in 6, and increased in 1. No patient exhibited permanent radiation injury. Grade 2 nausea and vomiting according to the Common Terminology Criteria for Adverse Events 4.0 occurred in 1 patient who received corticosteroids. CONCLUSIONS: Linac-based fSRT with a micro-multileaf collimator delivered in the doses of 24-40 Gy in 7-13 fractions is a safe and effective local therapy for patients with BSM.