Objective: The aim of this study was to characterize clinical and histopathological features, and management outcomes of patients with oral immune-related adverse events (irAEs) secondary to programmed cell death-1 (PD-1) inhibitors.

Methods: This was a case series of cancer patients receiving PD-1 inhibitor therapy who were referred to oral medicine for the development of oral irAEs. Demographic, clinical, and histopathological data were collected from electronic medical records.

Results: There were 13 patients (7 males) with a median age of 68 years (range: 39-82) who were treated with nivolumab (n = 7) or pembrolizumab (n = 6). Oral irAEs included lichenoid lesions (n = 10), erythema multiforme (EM) (n = 2), and acute graft-versus-host disease reactivation (n = 1), with or without ulcerations (n = 8). Four patients (31%) presented with only oral irAEs. Oral biopsies showed lichenoid mucositis (n = 4). Management with topical and systemic steroids led to complete symptomatic response in most patients (n = 12). PD-1 inhibitor therapy was temporarily discontinued (n = 3) and discontinued indefinitely (n = 2) due to severe oral irAEs.

Conclusion: Patients receiving PD-1 inhibitors may develop oral irAEs characterized by lichenoid lesions, ulcers, or EM. Topical and systemic steroids appear to be effective in managing oral lesions although the severity of irAEs may necessitate PD-1 inhibitor therapy dose modification.