Neutrophil-to-lymphocyte ratio as a predictor of immune checkpoint inhibitor therapy response in advanced bladder cancer

e16586 Background: Immune checkpoint inhibitor (ICI) therapy is a novel and promising agent for treating muscle invasive bladder cancer (MIBC). However, there is a need for further understanding of which patient factors or biological markers can be used to help identify patients who will have a successful response to ICI therapy. We hypothesized that Neutrophil-to-Lymphocyte Ratio (NLR) could be predictive of response to ICI therapy as this ratio has previously been reported to correlate with a higher number of myeloid derived suppressor cells. Methods: A retrospective cohort analysis was performed on patients with advanced or metastatic bladder cancer who were treated with ICI therapy at a single institution between 2015-2020. Information on survival, disease recurrence, and patient characteristics was gathered. Neutrophil and lymphocyte numbers were recorded at time of ICI administration and a ratio of neutrophils to lymphocytes was calculated. The median of these values was calculated and used to divide the cohort into low NLR and high NLR. Tissue samples from a subset of these patients were collected and sent for multiplex immunohistochemistry with a myeloid and T cell staining panel. Results: In a cohort of 115 patients with advanced bladder cancer treated with ICI, the mean time to last follow up or event (death or disease progression) was 375.78 days (SD 41). 35 patients (30%) had either a complete or partial response to ICI therapy. A Kaplan Meier survival analysis shows a significant difference in survival between the low and high NLR group, with lower NLR having a longer event free survival (Wilcoxon rank p = 0.0156). Multiplex IHC showed variable tumor and adjacent microenvironmental distributions of myeloid and lymphoid marker positive populations in ICI responders and non-responders. Conclusions: In an effort to better predict which patients may benefit from ICI therapy, we have studied NLR at the time of ICI administration and its association with event free survival. Our results suggest that a lower NLR could be associated with a longer event free survival. Further research is being conducted to study the immune microenvironment as it relates to bladder cancer response to ICI therapy.