The role of pre- and post-SRS systemic therapy in patients with NSCLC brain metastases

Purpose: We report our experience with stereotactic radiosurgery (SRS) for NSCLC brain metastases. We then assess the prognostic value of pre- and post-SRS systemic therapy (PrSST and PoSST) and evaluate the timing of PoSST. Methods: In this retrospective study, we analyzed 96 patients with lung cancer and ECOG PS ≤ 3 who underwent SRS during 2007-2013. Recorded factors included SRS treatment parameters, systemic status of disease (SDS) at time of SRS, and the use of PrSST and PoSST. SDS was designated as pulmonary disease or extrapulmonary disease. For analysis, the SRS-PoSST interval (SPI) was divided into ≤30 days and >30 days. Univariate and multivariate analyses were performed. Results: 85 patients with NSCLC were included in this analysis. 48% received PrSST and 48% received PoSST. 57% of patients had pulmonary disease while 40% had extrapulmonary disease. 46% of patients had synchronous metastases. At a median follow-up of 6 months, the median survival was 6.4 months and the actuarial overall survival at 3, 6, 12, and 36 months was 80%, 52%, 31%, and 6%. Extrapulmonary disease (p = 0.008) negatively predicted for survival while the receipt of any systemic therapy (p = 0.050) or PoSST alone (p = 0.039) positively predicted for survival. In patients receiving PoSST, an SPI >30 days positively predicted for survival (HR 0.28, 95% CI 0.13-0.62, p = 0.002) regardless of SDS. Conclusion: Our results indicate the prognostic importance of systemic therapy and specifically PoSST. Additionally, delaying the initiation of PoSST to >30 days seems beneficial. This finding was potentially influenced by neurotoxicity after SRS. Further investigation is warranted to define the optimal SPI.