Incidence of oral reactions of immune-related adverse events caused by immune checkpoint inhibitors

Immune-related adverse events (irAEs) are side effects caused by the persistence of autoantigen-specific T cells in normal cells and organs that are not eliminated after immune checkpoint inhibitors (ICI) administration. Oral irAEs include xerostomia, oral mucositis, and lichen planus-like lesions; however, only a few studies have reported oral irAEs during ICI therapy. This study aimed to examine the incidence of oral irAEs in our hospital and the effect of oral care. The study enrolled 165 patients who underwent oral hygiene management during ICI administration, and did not undergo radiotherapy to the head and neck region, and 63 patients (38.2 %) presented with oral mucositis and/or xerostomia, which appears to be oral irAE. Although most of the patients who suffered from these oral reactions were using anti-Programmed cell Death-1 antibodies, severe oral mucositis was observed in patients who treated with multiple ICIs. Symptoms of patients with grade 1 and 2 mucositis were improved with oral care, and ICI were continued in most of them. However, all patients with grade 3 oral mucositis also showed improvement in symptoms, ICI therapy was discontinued in three patients, systemic steroids were administered in two patients, and ICI therapy was not restarted during the study period. The incidence of oral irAEs is high in patients on ICI therapy, and continuous oral hygiene management by experts appears to be important for continuity of the treatment.