Change in the Neutrophil-to-Lymphocyte Ratio (NLR) Pre and Post Stereotactic Body Radiation Treatment (SBRT) for Stage I Non-Small Cell Lung Cancer (NSCLC): Is There a Clinical Significance?

Abstract

Pre-treatment systemic inflammatory markers such as elevated neutrophil-to-lymphocyte ratio (NLR) have previously been shown to be poor indicators in various cancers including NSCLC. However, there is a poor understanding of the effect of SBRT on post-treatment NLR and lymphocyte nadir and its prognostic implication, if any. The purpose of this study was to assess the effects of SBRT on NLR and lymphocyte nadir, and the predictive value of post-SBRT NLR and lymphocyte nadir on tumor response and progression-free survival in stage I NSCLC patients. From our institutional database between 2015-2016, we identified 43 patients with AJCC Stage I NSCLC who underwent definitive SBRT treatment with a median dose of 50 Gy (range 50-55 Gy) over a 2-week period. We collected demographic and clinical data including: age, gender, baseline and post-treatment (last day of treatment) bloodwork (platelet, neutrophil, and lymphocyte counts), initial response to SBRT, and 1-year progression-free-survival (PFS). Median age of patients was 76.4 (range 42.5-96.4). Median follow up for patients was 11.8 months. Of the 43 patients, at 1 year, 91% of patients did not show any progression, while 9.0% patients demonstrated distant progression. Median pre-SBRT NLR was 3.9 (mean 5.2) and median post-SBRT NLR was 5.2 (mean 6.4), demonstrating a 33.3% increase in NLR post-SBRT treatment (p<.05) on their last day of treatment. Median lymphocyte count pre-SBRT was 1.31 (mean 1.29) and median post-SBRT lymphocyte nadir was 0.83 (mean 0.87), demonstrating a 36.6% decrease (p<.001). There was a significant difference in pre-SBRT NLR (6.28 vs. 3.96, p<.01) and post-SBRT NLR (7.47 vs. 5.41, p<.05) in patients demonstrating a partial vs. complete response to SBRT. Lymphocyte nadir changes were nonsignificant in patients demonstrating partial and complete response. Additionally, there were significant differences in pre-SBRT NLR (4.15 vs. 8.71, p<.005) and post-SBRT NLR (6.02 vs. 9.24, p<.01) in patients who did not progress at 1 year and those progressed at 1-year. Pre-SBRT lymphocyte nadir (1.91 vs. 1.20, p<.001) and post-SBRT lymphocyte nadir (0.92 vs 0.71, p<.01) was also decreased in patients with progression compared to those without progression at 1 year. Pre and post-SBRT NLR and lymphocyte nadir was not associated with increased toxicity. SBRT resulted in a statistically significant increase in NLR ratio and decreased lymphocyte nadir. Furthermore, our study indicates increased NLR and decreased lymphocyte nadir both pre-SBRT and post-SBRT can help predict tumor response to SBRT and progression outcomes. Clinical significance of this sudden change following SBRT treatment needs further study.