Natural history of lung squamous cell brain metastases in patients treated with radiosurgery: a thirty-year experience at a tertiary medical center

Purpose: In this study we report our 30-year experience in stereotactic radiosurgery (SRS) treatment of lung squamous cell carcinoma (LUSC) brain metastases (BMs). It will serve to provide detailed longitudinal outcomes and predictors of efficacy in treating LUSC-BMs with SRS. Method: We retrospectively reviewed 51 patients and 109 tumors treated with SRS at our center between 1993 and 2022. Patient demographics, PDL1 genotype, immunotherapy use and mortality cause were recorded. Radiological and clinical outcomes were followed at 1-3-month intervals post-SRS. Cox-regression analysis and Kaplan-Meier survival curves were performed in statistical analysis. Results: We included 37 male and 14 female patients (median age 62.7 years at BM diagnosis). Median overall survival (OS) time was 6.9 months, 6-month OS rate was 62.1%, and Karnofsky performance scale (KPS) was the only independent predictor. Median time for local control maintenance was 7.6 months, 6-month local control rate was 69.1%, with TKI as the only independent predictor. Median time to distant failure was 5.13 months, 6-month distant failure rate was 51.1%, and factors with significant impact included gender (p = 0.002), presence of extracranial metastases (p < 0.001), use of immunotherapy(p < 0.001), PDL1 genotype (p = 0.034), and total intracranial metastases number (p = 0.008). However, no definitive benefits of immunotherapy were identified in patients with higher PDL1 mutational tumors. Conclusion: In this study we defined the natural history of disease progression and outcomes in SRS-treated LUSC-BM patients. We also identified predictors of OS and tumor control among these patients. The findings of this study will serve as a guide when counseling these patients for SRS.