Clinical outcome after CyberKnife® radiosurgery re-irradiation for recurrent brain metastases

The objective of this study was to elucidate the impact on clinical outcomes resulting from re-irradiation for locally recurrent (LR) brain metastases (BM) using CyberKnife® stereotactic radiosurgery (SRS).

Seventy-seven patients with 254 LR BM lesions treated using SRS re-irradiation between January 2014 and December 2018 were analysed in this retrospective study. The local control (LC), overall survival (OS) rates, and adverse events were assessed. The adverse events were classified according to the Common terminology for adverse event (CTCAE) v5.0.

The median follow-up duration was 8.9 months. The median age of the patients was 55 years (IQR: 47-62). The 3, 6, and 9-month LC and OS rates were 92.2%, 73.4%, and 73.4% and 79.2%, 61.0%, and 48.1%, respectively. On multivariate analysis the gender (male vs. female; HR, 1.79; 95% CI, 1.06-3.01; P=0.028), type of first brain radiation (WBI vs. SRS) followed by re-irradiation using SRS (HR, 9.32; 95% CI, 2.77-15.27; P<0.001) tumour volume (>12cc vs. ≤12cc; HR, 1.84; 95% CI, 1.10-3.11; P=0.02), and recursive partitioning analysis (RPA) (I vs. II & III; HR, 0.38; 95% CI, 0.19-0.70; P=0.001) were independent predictive factor for OS. Radionecrosis was reported in 3 patients.

With acceptable toxicity, SRS re-irradiation for LR BM showed a favourable rate for LC and OS and reported better OS for the female gender, a patient undergoing first brain radiation with SRS, tumour volume ≤12cc, and RPA-I. This result needs to be further evaluated in future clinical studies.