Frameless, real-time, surface imaging-guided radiosurgery: update on clinical outcomes for brain metastases

Frameless stereotactic radiosurgery (SRS) for intracranial brain metastases can provide more comfortable treatment setup than rigid frame-based immobilization with equivalent accuracy. The aim of this study is to report the UCSD SRS experience and update the clinical outcomes using a novel real-time, frameless, surface imaging-guided (SIG-RS) technique in the treatment of brain metastases. Data were retrospectively examined for 163 patients totaling 490 lesions and 45 post-operative cavities treated with SIGRS in a median delivery of 1 fraction (range, 1-5 fraction) and to a median dose of 22 Gy (range, 12-30 Gy). Local control and overall survival were estimated by the Kaplan-Meier method. Median follow-up for all patients was 6.7 months (range, 0.5-45.1 months), with 119 of 163 (73%) deceased at the time of analysis. The 134 patients (82%) with follow-up imaging studies totaling 378 lesions and 39 post-operative cavities were evaluated for local control. The actuarial 6- and 12-month local control was 90% [95% confidence interval (CI), 84-94%] and 79% (95% CI, 71-86%), respectively. The actuarial 6- and 12-month overall survival was 80% (95% CI, 74-85%) and 56% (95% CI, 49-63%), respectively. There is no significant difference in local control between treatment to post-operative cavities or intact lesions. Consistent with our earlier report of 44 patients, SIG-RS for treatment of intracranial metastases can produce outcomes comparable to those with conventional frame-based and frameless SRS techniques while providing greater patient comfort with an open-faced mask and fast treatment time.