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BACKGROUND Stereotactic Radiosurgery (SRS) has become a primary management option for brain metastases (BMs). This present study aims to review outcomes in patients with ≥ 20 BMs treated in a single session SRS and to identify predictors of local tumor control (LTC) and overall survival (OS). METHODS We identified 75 patients including 26 non-small cell lung cancer (NSCLC), 21 small cell lung cancer (SCLC), 14 breast cancer (BC), and 14 melanoma patients who underwent SRS for ≥ 20 BMs between 2014 and 2020. The median number of tumors was 24 (range 20 – 52), and the median cumulative tumor volume was 3.70 cc (0.13 – 62.49 cc). The median margin dose was 16 Gy (14 – 20 Gy). Median skull integral dose was 5492 mJ (range 1372 – 11243 mJ). The median treatment time for each session was 160 min. Outcome variables were assessed using univariate and multivariate analyses with p < 0.05. RESULTS Median OS after SRS was 5.8 months (range 0.1 – 73.2 months). Primary cancer type and concurrent immunotherapy were significant predictive factors for patient OS after SRS (p = 0.01, 0.05, and 0.02, respectively). LTC rate at 6 and 12 months after SRS was 95.7% and 83.7%, respectively. Thirty (40.0%) patients underwent additional SRS and 3 patients (4%) received post-SRS WBRT due to distant tumor recurrence. The median time to distant recurrence was 5 months (range 2-28 months). SRS-induced adverse radiation effects (ARE) events were observed in 3 patients (4.0%; 1 NSCLC, 1 SCLC, and 1 melanoma). CONCLUSIONS Our results suggest that patients with ≥ 20 BMs can be safely treated with SRS with an excellent LTC rate and a low risk of ARE. Newly developed BMs can be treated with repeat SRS. This single-session SRS allows patients to proceed with systemic cancer care without interruption.

BACKGROUND: Stereotactic radiosurgery (SRS) is a widely accepted treatment modality for brain metastases. The role of SRS in patients with higher numbers of metastases remains controversial. OBJECTIVES: To define outcomes in patients with ≥20 brain metastases managed using single-session SRS. METHODS: This single-institution retrospective cohort study studied 75 patients (26 non–small-cell lung cancer, 21 small-cell lung cancer, 14 breast cancer, and 14 melanoma) undergoing single-session SRS. The median number of tumors per patient was 24, and the median cumulative tumor volume was 3.70 cc. The median margin dose prescribed to each individual tumor was 16 Gy. The median integral cranial dose was 5492 mJ. The median beam on time was 160 minutes. Univariate and multivariate analyses were performed with significance set at P < .05. RESULTS: The median overall survival after SRS was 8.8 months (patients with non–small-cell lung cancer), 4.6 months (patients with small-cell lung cancer), 11.3 months (patients with breast cancer), and 4.1 months (patients with melanoma). Primary cancer type, number of brain metastases, and concurrent immunotherapy were significant factors in predicting survival. Local tumor control rate per patient was 97.3% and 94.6% at 6 and 12 months after SRS, respectively. Thirty-six patients underwent additional SRS for new tumor development with a median time after SRS of 5 months. Three patients experienced adverse radiation events. CONCLUSION: Single-session SRS is a well-tolerated palliative treatment option even in patients with ≥20 brain metastases, achieving local control rate >90% with low risks of neurotoxicity while continuing concurrent systemic oncological care.