522 Associations between influenza vaccine and immunotherapy outcomes in metastatic melanoma patients

Abstract

Immune checkpoint inhibitors (ICI) elicit antitumor response in 30-50% of metastatic melanoma (MM) patients. Prior studies have implicated a decreased melanoma risk and enhanced immune response with influenza vaccination. However, associations between this vaccine and patient outcomes on ICI, including immune-related adverse events (irAEs), progression-free survival (PFS), and overall survival (OS) are unclear. We performed a single institution, retrospective cohort analysis characterizing influenza vaccination patterns in MM patients receiving ICI. Inclusion criteria included newly diagnosed stage IV or unresectable stage III MM patients who received ICI as first-line systemic treatment from 2013-2018 and had vaccination records. With a vaccinated cohort of 90 patients and unvaccinated cohort of 86 patients, median age of vaccinated patients was significantly higher compared to unvaccinated at the initiation of ICI (70 vs 59 years; p<0.0001). Vaccinated patients were more likely to receive single agent anti-PD1 therapy (68% vs 38%; p=0.0003). IrAEs were more prevalent in the vaccinated cohort compared to the unvaccinated cohort (67% vs 40%; p=0.0005), predominantly due to cutaneous irAEs (61% vs 34%; p=0.0002). Both cohorts stopped ICI most often due to disease progression, but this was less common for the vaccinated cohort (46% vs 64%; p=0.03). Vaccinated patients had longer PFS than unvaccinated (HR=0.67; 95% CI, 0.47-0.97), but not OS (HR=0.95; 95% CI, 0.62-1.46). Overall, 51% of patients received the recommended flu vaccination prior to ICI. Vaccinated patients experienced a higher rate of irAEs yet had a higher PFS compared to unvaccinated patients. Larger cohorts are necessary to explore further associations between this simple, universally recommended preventative health adjunct and potentially improved ICI outcomes in MM patients.