Timing of steroid use and outcomes of immune checkpoint inhibitor: A population based study.

6590 Background: Immune checkpoint inhibitors (ICIs) have rapidly become the treatment of choice for multiple cancer types. However, the relationship between the timing of immunosuppressive agents, such as steroids use, preceding ICI initiation and subsequent treatment outcomes remains unknown due to lack of data. This study was undertaken to address this knowledge gap. Methods: We used the Surveillance, Epidemiology and End Results (SEER)-Medicare linked data to identify patients with melanoma receiving Ipilimumab, Nivolumab, Pembrolizumab, or Ipilimumab/Nivolumab combination in 2010-2015. Last steroid exposure within 12 months prior to ICI use was categorized (none, 0-1, 1-3, and 3-12 months prior). Cox models were used to generate covariate-adjusted hazard ratios of overall mortality following ICI initiation. Because the hazards were not proportional over time, we allowed the hazard ratios to differ in three periods (<3, 3-6, and more than 6 months post ICIs). Results: We identified 3,149 melanoma patients (median age 68 years) using ICIs; among these 1,352 received steroid within 12 months prior. Steroid use within 1 month prior to using ICIs was associated with a 93% and 102% increased risk in overall mortality within 3 months and 3-6 months post ICI initiation. The risk diminished over time (Table). A similar pattern was observed for steroid use 1-3 months prior. Steroid use beyond 4 months prior to ICI was not associated with increased mortality. Conclusions: This was the first major study to document that timing of steroid use prior to ICI is associated with the risk of mortality and how the increased risk diminishes over time. Further studies are warranted to confirm the findings and understand potential mechanisms.[Table: see text]