Frameless stereotactic radiosurgery for brain metastases: a review of outcomes and prognostic scores evaluation.

Introduction: Stereotactic brain radiosurgery provides good local control in patients with limited brain metastases. A newly developed frameless system allows pain-free treatment. We reviewed the effectiveness of this frameless stereotactic brain radiosurgery and identified prognostic factors that may aid better patient selection.
Methods: Medical records of patients with brain metastases treated with linear accelerator-based frameless stereotactic brain radiosurgery between January 2010 and July 2015 in a university affiliated hospital in Hong Kong were reviewed. Outcomes including local and distant brain control rate, progression-free survival, and overall survival were analysed. Prognostic factors were identified by univariable and multivariable analyses. Association of outcomes with four common prognostic scores was performed.
Results: In this study, 64 patients with 94 lesions were treated with a median dose of 18 Gy (range, 12-22 Gy) in a single fraction. The median follow-up was 11.5 months. One-year actuarial local and distant brain control rates were 72% and 71%, respectively. The median overall survival was 13.0 months. On multivariable analysis, Karnofsky performance status score (>50 vs ≤50) and number of lesions (1-2 vs ≥3) were found to associate significantly with distinct brain progression-free survival (P=0.022, hazard ratio=0.20, 95% confidence interval 0.05-0.80 and P=0.003, hazard ratio=0.31, 95% confidence interval 0.14-0.68, respectively). Overall survival was associated significantly with Basic Score for Brain Metastases (P=0.031), Score Index for Radiosurgery in Brain Metastases (P=0.007), and Graded Prognostic Assessment (P=0.003). Improvement in overall survival was observed in all groups of different prognostic scores.
Conclusion: Frameless stereotactic brain radiosurgery is effective in patients with oligo-metastases of brain and should be increasingly considered in patients with favourable prognostic scoring.