Incidence and Timing of Immune-Related Adverse Events in Immune-Checkpoint Inhibitor-Treated Patients: A Retrospective Observational Study.

Background: Immune-checkpoint inhibitors (ICIs) are effective against various cancers; however, immune-related adverse events (irAEs) have been reported and the timing and risk factors are unknown. Therefore, we examined the incidence and timing of irAE occurrence.
Methods: Patients who received ICIs at our hospital between 1 April 2016 and 31 March 2020 were enrolled. Patients were classified into an irAE group or non-irAE group. In addition, we examined the onset time and symptoms of irAEs for each ICI type.
Results: A total of 80 patients received ICIs, of which 27 (33.8%) developed irAEs. The incidence of irAEs was 35.3% for nivolumab, 35.5% for pembrolizumab, and 28.6% for atezolizumab. The incidence of pneumonitis was 12.5%, 8.8% for dermatologic adverse events, and 6.3% for thyroid dysfunction. The earliest case of onset was after the 1st course, and the latest cases occurred after the 66th course. By the sixth course, 69% of the irAEs occurred. The positive rates for anti-thyroid peroxidase and anti-thyroglobulin antibodies were higher in the irAE group compared to the non-irAE group.
Conclusions: Our findings suggest a high probability of irAEs occurring early in ICI treatment, with a diverse range of symptoms. This underscores the need for vigilant monitoring and tailored patient management during the initial courses of ICI therapy.