Real-world evidence of the impact of prior antibiotic exposure on immune checkpoint inhibitor outcomes in patients with metastatic urothelial cancer.

Abstract

452 Background: Prior research suggests that systemic antibiotic (ABX) exposure may impact gut microbiome and potentially result in suboptimal immune checkpoint inhibitor (ICI) treatment outcomes. A recent real-world analysis demonstrated that cumulative ABX exposure was associated with poorer outcomes across multiple tumor types independent of known prognostic clinical factors. Given the paucity of real-world data, we set out to evaluate the association of prior ABX exposure with ICI treatment outcomes among patients with metastatic urothelial cancer (mUC). Methods: This was a retrospective analysis using Truven Health MarketScan Commercial, Medicare Supplemental, and Coordination of Benefits (Medicare) databases. Patients with mUC, ≥18 years old, who received first line (1L) ICI therapy between 1/1/2016 and 12/31/2018 were analyzed. Prior ABX exposure was defined as any use in the 90 days prior to 1L ICI therapy initiation. Time to treatment discontinuation was used as a proxy to quantify ICI treatment outcomes. Results: Among the 304 ICI treated patients, 128 (42%) had ABX exposure within 90 days prior to ICI initiation. Statistically significant differences in baseline co-morbidities and urinary tract infections (36% vs. 17%; p<0.001) were observed between patients with vs. without ABX exposure. The median time to treatment discontinuation was shorter for patients with ABX exposure (7.9 months) vs. without (9.3 months). In adjusted regression analysis, there was no statistically significant difference in time to treatment discontinuation between patients with vs. without ABX exposure (p=0.95). These findings were consistent in a sensitivity analysis looking at ABX exposure 30 and 60 days prior to 1L ICI initiation. Conclusions: In this real-world analysis of patients with mUC, those with ABX exposure within 90 days prior to 1L ICI initiation demonstrated similar outcomes to those without ABX exposure. While there was a shorter time to treatment discontinuation in the patients with vs. without ABX exposure, findings were not statistically significant. Further research is warranted to investigate the impact of concomitant ABX use on ICI outcomes.