Objective: Immune checkpoint inhibitors (ICIs) have been widely used in cancer treatment; however, some case reports suggested that ICIs treatment might result in ileus. This study aims to comprehensively reveal the relationship between ileus and ICIs treatment in real-world cases from Food and Drug Administration (FDA) Adverse Event Reporting System (FAERS).

Methods: Reports from January 1, 2011 to December 31, 2020 were extracted from the FAERS. ICIs-related adverse events in patients were defined as related to use of anti-programmed cell death protein 1 antibodies (PD-1, nivolumab and pembrolizumab), anti-programmed cell death-ligand 1 inhibitors (PD-L1, atezolizumab, durvalumab, avelumab, and cemiplimab), and anti-cytotoxic T-lymphocyte-associated protein 4 (CTLA-4, ipilimumab and tremelimumab). ICIs-related ileus cases were identified to characterize their clinical features. Reporting odds ratios (ROR) and information component (IC) were used to assess the relationship between ICIs and ileus.

Results: Among the 105 001 cases related to ICIs, 245 were reported with ICI-related ileus. The affected patients were mainly elderly (median age, 64.5 years) and male (58%, n = 143). The median onset for all cases was 36 (range 0-880) days, and no statistical difference was observed between monotherapy and combination therapy (PD-1 or PD-L1 plus CTLA-4) (p = 0.21). Most patients required drug withdrawal treatment (n = 113, 74%) and can achieve a recovered-resolved state (n = 72, 46%). All ICIs were significantly associated with ileus (ROR = 4.27, 95%Cl: 3.75-4.85; IC = 2.04, 95%Cl: 1.79-2.31). Ileus events were most commonly reported in PD-1 treatment (n = 164, ROR = 3.83, 95%Cl: 3.28-4.48; IC = 1.90, 95%Cl: 1.62-2.21).

Conclusion: This pharmacovigilance database analysis suggested that ICIs are related to ileus. However, combination therapy may not speed up the onset of ileus.