Pre-stereotactic radiosurgery neutrophil-to-lymphocyte ratio predicts post-stereotactic radiosurgery survival of patients with brain metastases concurrently treated with immune checkpoint inhibitors.

Objective: Treatment with immune checkpoint inhibitors (ICIs) has shown clinical benefit for a wide range of cancer types. The neutrophil-to-lymphocyte ratio (NLR) reportedly correlates with survival time or progression-free survival in patients treated with ICIs. However, NLR has not yet been assessed in patients with brain metastases (BMs) receiving stereotactic radiosurgery (SRS) combined with concurrent ICIs. The authors investigated the predictive impact of NLR on the survival data of patients with BMs who received SRS with concurrent ICIs.

Methods: The clinical records of patients who had undergone SRS with concurrent ICIs for BMs between January 2015 and August 2023 were retrospectively analyzed. NLR was calculated using the data obtained from the last examination prior to SRS. The optimal NLR cutoff value was identified by receiver operating characteristic (ROC) curve analysis for time-to-event data (overall survival [OS] ≤ 18 months). OS and intracranial disease progression-free survival (IC-PFS) rates were compared between the two NLR groups.

Results: Of the 185 eligible patients included, 132 were male. The median (IQR) patient age was 69 (61-75) years. The primary cancers were lung, genitourinary, skin, breast, gastrointestinal, and others in 132, 23, 22, 2, 2, and 4 patients, respectively. The post-SRS median OS and IC-PFS times for the entire cohort were 18.4 (95% CI 14.0-23.1) months and 9.2 (95% CI 6.9-10.8) months, respectively. ROC curve analysis identified the optimal NLR cutoff value for 18-month OS to be 5.0 (area under the curve 0.64, Youden index 0.31). Kaplan-Meier analysis revealed that patients with high NLR (> 5) had a significantly shorter OS (median survival time 10.9 months for 48 patients vs 22.2 months for 137 patients, HR 2.0, 95% CI 1.3-3.0, p < 0.001). Similarly, a significant difference in median IC-PFS was noted: 4.8 months with high NLR versus 10.7 months with low NLR (HR 1.7, 95% CI 1.2-2.5, p = 0.003).

Conclusions: The authors found elevated pre-SRS NLR (> 5) to be associated with shorter OS and IC-PFS after SRS with concurrent ICIs for BMs. NLR is a simple, cost-effective, and widely accessible biomarker, which can thus be used for managing patients with BMs receiving SRS concurrently with ICIs. Further investigation in other large datasets is, however, required to validate these findings.