Is White Blood Cell Count a Predictor of Immune-Related Adverse Events and Favorable Prognosis in the Gastric Cancer Patients Treated with Nivolumab?

Introduction: Immune-related adverse events (irAEs) have been reported to be a favorable prognostic factor in patients treated with immune checkpoint inhibitors. To identify the convenient biomarkers to predict irAEs, we analyzed the relationship between pretreatment laboratory data and irAEs in gastric cancer patients treated with nivolumab. Methods: A retrospective analysis was performed on 38 patients treated with nivolumab for unresectable or recurrent gastric cancer between September 2017 and December 2019. We evaluated the relationships between pretreatment laboratory data, adverse events, and prognosis. The significance of irAE predictors was evaluated via univariate and multivariate analyses. The prognostic significance of irAE predictors was also evaluated. This study was approved by the relevant ethics committee of Toho University Omori Medical Center (No. M21048, 20108, M20300). Results: In total, 14 irAEs were recorded in 13 of 38 patients (37%). The irAE (+) group showed favorable treatment response (P = 0.038) and prognosis (P = 0.093) in comparison with the irAE (-) group. The irAE (+) group showed low urea nitrogen, high sodium, and low white blood cell count (less than 5100/μl). Although low urea nitrogen and high sodium were identified to be not associated with good overall survival, the group with low white blood cell count was significantly associated with good overall survival (P = 0.022). Conclusions: A low white blood cell count at pretreatment may be a predictor of irAEs and favorable overall survival in gastric cancer patients treated with nivolumab. Gastric cancer patients with a low white blood cell count may be a good candidate for nivolumab treatment.