Stereotactic Radiosurgery for 1-10 Brain Metastases to avoid Whole-Brain Radiotherapy - Results of the CYBER-SPACE Randomized Phase 2 Trial

Background: Stereotactic Radiosurgery (SRS) is an emerging alternative to whole-brain radiotherapy (WBRT) for treating multiple brain metastases (BM), reducing toxicity and improving tumor control. The CYBER-SPACE trial compared SRS based on either SPACE or MPRAGE MRI sequence for avoiding or delaying WBRT in patients with 1-10 BM.

Methods: Patients with 1-10 untreated BM were randomized 1:1 to receive SRS of all lesions based on either SPACE or MPRAGE MRI sequences. If subsequently new BM occurred, SRS was repeated. WBRT was indicated upon occurrence of >10 new BM, leptomeningeal disease or exhausted SRS-radiotolerance. The primary outcome was freedom from WBRT indication (WBRTi). Secondary outcomes included overall survival (OS), safety, and quality of life.

Results: 202 patients were randomized; SPACE n=99, MPRAGE n=103. 12-month WBRTi-free survival was 77.1% (95%-CI: 69.5%-83.1%) overall, 78.5% (95%-CI: 66.7%-86.5%) for SPACE, and 76.0% (95%-CI: 65.2%-83.9%) for MPRAGE (HR=0.84, 95%-CI: 0.43-1.63, p=0.590). Patients with 5-10 BM had shorter WBRTi-free survival (HR=3.13, 95%-CI: 1.53-6.40, p=0.002). Median OS was 13.1 months overall, 10.5 months for SPACE, and 15.2 months for MPRAGE (HR=1.10, 95%-CI: 0.78-1.56, p=0.585). Neurologic death rate was 10.1%. Predictors for longer OS included Karnofsky Performance Status >80% (HR=0.51, 95%-CI: 0.33-0.77, p=0.002) and concurrent immunotherapy (HR=0.34, 95%-CI: 0.23-0.52, p<0.001).

Conclusions: The more sensitive SPACE sequence did not improve outcomes over MPRAGE. SRS with thorough monitoring and immediate re-treatment for new lesions decreases the need for WBRT and achieves low neurologic death rates. SRS should be considered a favorable alternative to WBRT for patients with 1-10 BM.