Survival Outcomes of Gamma Knife Radiosurgery in EGFR -Mutant Non-Small Cell Lung Cancer Patients With 1–4 Versus 5–10 Brain Metastases: A Vietnamese Study

BackgroundIn the targeted therapy era, the indication for stereotactic radiosurgery (SRS) has expanded to include patients with multiple brain metastases (BMs).This study aimed to compare treatment outcomes in epidermal growth factor receptor (EGFR)-mutant non-small cell lung cancer (NSCLC) patients with 1-4 versus 5-10 BMs, all treated with tyrosine kinase inhibitors (TKIs) and upfront Gamma Knife radiosurgery. MethodsWe retrospectively reviewed 74 consecutive EGFR-mutant NSCLC patients with 1-10 synchronous BMs treated with first-line EGFR-TKIs and upfront Gamma Knife SRS at Vietnam National Cancer Hospital from 2021 to 2024.Patients were divided into 1-4 BMs (n=39) and 5-10 BMs (n=35) groups.Primary endpoints were intracranial progression-free survival (iPFS) and overall survival (OS). ResultsBaseline characteristics were balanced between the two groups.Median iPFS was not reached in the 1-4 BMs group and 19 months in the 5-10 BMs group (hazard ratio [HR] 1.06, 95% confidence interval [CI] 0.95-1.17;p=0.31).Median OS was not reached in the 1-4 BMs group and was 23 months in the 5-10 BMs group (HR 1.03, p=0.41).Multivariate analysis revealed extracranial response (HR 4.30, p<0.01 for iPFS; HR 7.29, p<0.01 for OS) and presence of extracranial metastases (HR 3.20, p=0.01 for iPFS) as the only independent prognostic factors; number of BMs was not prognostic.Radionecrosis occurred in 6.8%, of which 2.7% were symptomatic. ConclusionIn EGFR-mutant NSCLC patients receiving TKIs and upfront Gamma Knife radiosurgery, the survival time in patients with 5-10 BMs was comparable to that with 1-4 BMs.The number of BMs should not be regarded as a contraindication for SRS in this subgroup.