Safety and efficacy of retreatment with immune checkpoint inhibitors after severe immune-related adverse events

Background While immune checkpoint inhibitors (ICIs) have revolutionized cancer treatment, they can trigger severe immune-related adverse events (irAEs). The safety and efficacy of ICI retreatment after severe irAEs remain poorly understood. Methods We conducted a retrospective analysis of 1271 patients with malignancies treated with ICIs at a university hospital in Japan between September 2014 and June 2023. We evaluated the incidence and characteristics of severe irAEs, defined as grade ≥3, and the safety and efficacy of ICI retreatment. Results Severe irAEs occurred in 222 patients (17.5%). Patients with single endocrinopathies were excluded, and 46 (28.4%) of the remaining 162 patients underwent ICI retreatment. Upon retreatment, 14 patients (30.4%) experienced recurrent or new grade ≥2 irAEs. One patient who experienced hepatotoxicity (grade 3) at initial ICI treatment developed a recurrence (grade 4). Regarding antitumor response, the objective response rate to retreatment was 28.3% (13/46), with 10.9% achieving complete and 17.4% partial response. The median duration of ICI administration after retreatment was 218 days (95% confidence interval [CI]: 84-399). At 1 year after retreatment, 15.4% (95% CI: 6.8-27.4) of patients discontinued due to irAEs, 44.4% (95% CI: 29.7-58.1) due to disease progression, 6.6% (95% CI: 1.7-16.3) completed planned treatment, and 33.4% (95% CI: 20.3-47.2) continued treatment. Conclusions ICI retreatment after severe irAEs demonstrated a manageable safety profile and promising efficacy, even in patients with grade ≥3 irAEs. ICI retreatment may be a viable option for patients with limited alternatives, particularly those showing favorable antitumor responses at initial treatment.