Introduction: Stereotactic radiosurgery (SRS) is an emerging treatment for patients with multiple brain metastases (BM). The present work compares the SRS of multiple brain metastases with whole-brain radiotherapy (WBRT).
Methods: We performed a matched-pair analysis for 128 patients with multiple BM treated with either SRS or WBRT over a 5-year period. Patients were matched pairwise for seven potential prognostic factors. A mixed Cox Proportional Hazards model with univariate and multivariate analysis was fitted for overall survival (OS). Distant intracranial progression-free survival (icPFS) and local control were assessed using a Fine and Gray subdistribution hazard model and considering death as competing event.
Results: Patients undergoing SRS had a median of 4 BM (range 3-16). 1-year local control of individual BM following SRS was 91.7%. Median OS in the SRS subgroup was 15.7 months (IQR 9.7-36.4) versus 8.0 months (interquartile range, IQR 3.8-18.0) in the WBRT subgroup (HR 2.25, 95% CI [1.5; 3.5], p < 0.001). Median icPFS was 8.6 (IQR 3.4-18.0) versus 22.4 (IQR 5.6-28.6) months, respectively (HR for WBRT 0.41, 95% CI [0.24; 0.71], p = 0.001). Following SRS, synchronous BM diagnosis (HR 2.51, 95% CI [1.30; 4.70], p = 0.004), higher initial number of BM (HR 1.21, 95% CI [1.10; 1.40], p = 0.002) and lung cancer histology (HR 2.05, 95% CI [1.10; 3.80], p = 0.024) negatively impacted survival. Excellent clinical performance (KPI 90%) was a positive prognosticator (HR 0.38, 95% CI [0.20; 0.72], p = 0.003), as was extracerebral tumor control (HR 0.48, 95% CI [0.24; 0.97], p = 0.040). Higher initial (HR 1.19, 95% CI [1.00; 1.40], p < 0.013) and total number of BM (HR 1.23, 95% CI [1.10; 1.40], p < 0.001) were prognostic for shorter icPFS.
Conclusion: This is the first matched-pair analysis to compare SRS alone versus WBRT alone for multiple BM. OS was prolonged in the SRS subgroup and generally favorable in the entire cohort. Our results suggest SRS as a feasible and effective treatment for patients with multiple BM.
Keywords: CyberKnife; Linear accelerator; Multiple brain metastases; Neurologic function; Palliative; Radiosurgery; Radiotherapy; Robotic; Stereotactic; Whole-brain radiotherapy.