Hypofractionated Stereotactic Radiotherapy for Intact Brain Metastases in 5 Daily Fractions: Impact of Dose on Treatment Response
Abstract
BACKGROUND
Multi-leaf collimator (MLC) linear accelerator (Linac) based hypofractionated stereotactic radiotherapy (HSRT) is increasingly practiced not only for large brain metastases or those adjacent to critical structures, but also for those metastases that would otherwise be considered for single fraction radiosurgery (SRS). However, outcomes in general are limited and there is a lack of understanding as to optimal dosing. Our aim was to report mature image-based outcomes for MLC-Linac HSRT with a focus on clinical and dosimetric factors associated with local failure (LF).
METHODS
220 patients with 334 brain metastases treated with HSRT were identified. All patients were treated using a 5-fraction daily regimen, and were followed with clinical evaluation and volumetric MRI every 2-3 months. Overall survival (OS) and progression-free survival (PFS) were calculated using the Kaplan-Meier method, with LF determined using Fine and Gray's competing risk method. Predictive factors were identified using Cox regression multivariate analysis.
RESULTS
Median follow up was 10.8 months. Median size of treated metastasis was 1.9 cm; 60% of metastases were 30 Gy. Exploratory analysis demonstrated a dose-response effect observed in all histologic types including amongst breast cancer sub-types.
CONCLUSION
Optimal local control is achieved with HSRT of ≥30Gy in 5 daily fractions independent to tumour volume and histology, with an acceptable risk of radiation necrosis.
How strong is the evidence?
Evidence Hub reads this as a cohort study, done in people. Its evidence level is 3 of 5 (Moderate · trial / cohort / secondary analysis). Trials without a large randomized design, cohorts and secondary analyses give moderate evidence. Reported size: 220 participants or records.
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