Post-treatment neutrophil-to-lymphocyte ratio predicts for overall survival in brain metastases treated with stereotactic radiosurgery.

Abstract

Neutrophil-to-lymphocyte ratio (NLR) is a surrogate for systemic inflammatory response and its elevation has been shown to be a poor prognostic factor in various malignancies. Stereotactic radiosurgery (SRS) can induce a leukocyte-predominant inflammatory response. This study investigates the prognostic impact of post-SRS NLR in patients with brain metastases (BM). BM patients treated with SRS from 2003 to 2015 were retrospectively identified. NLR was calculated from the most recent full blood counts post-SRS. Overall survival (OS) and intracranial outcomes were calculated using the Kaplan-Meier method and cumulative incidence with competing risk for death, respectively. 188 patients with 328 BM treated with SRS had calculable post-treatment NLR values. Of these, 51 (27.1%) had a NLR > 6. The overall median imaging follow-up was 13.2 (14.0 vs. 8.7 for NLR ≤ 6.0 vs. > 6.0) months. Baseline patient and treatment characteristics were well balanced, except for lower rate of ECOG performance status 0 in the NLR > 6 cohort (33.3 vs. 44.2%, p = 0.026). NLR > 6 was associated with worse 1- and 2-year OS: 59.9 vs. 72.9% and 24.6 vs. 43.8%, (p = 0.028). On multivariable analysis, NLR > 6 (HR: 1.53; 95% CI 1.03-2.26, p = 0.036) and presence of extracranial metastases (HR: 1.90; 95% CI 1.30-2.78; p < 0.001) were significant predictors for worse OS. No association was seen with NLR and intracranial outcomes. Post-treatment NLR, a potential marker for post-SRS inflammatory response, is inversely associated with OS in patients with BM. If prospectively validated, NLR is a simple, systemic marker that can be easily used to guide subsequent management.