Immune-related adverse events with immune checkpoint inhibitors: Insights from real-world practice in Brazil.

Abstract

e23338 Background: Immune checkpoint inhibitors (ICIs) are widely used in the treatment of multiple malignancies and are associated with a broad spectrum of immune-related adverse events (irAEs). Early recognition and appropriate intervention are critical for effective irAE management and to reduce treatment discontinuation in routine clinical practice. However, real-world data describing the incidence and patterns of irAEs remain limited. Methods: We conducted a retrospective, descriptive, single-center study using electronic medical records at a tertiary oncology center in São Paulo, SP, Brazil, to characterize patients treated with ICIs who developed irAEs between January 1, 2018, and December 31, 2025. Adult patients with histologically confirmed solid tumors who received at least one dose of an ICI, either as monotherapy or in combination (with another ICI and/or chemotherapy), were included. Patients with pre-existing autoimmune disease requiring immunosuppressive therapy, or receiving chronic systemic corticosteroids or other immunosuppressants at baseline for any indication, were excluded. irAEs were identified from clinical documentation and graded according to CTCAE v5.0. Descriptive statistics were used: categorical variables were summarized as counts and percentages, and continuous variables were summarized as median (interquartile range). Results: A total of 236 patients were included. The median age was 63 years (IQR 47–75), and 57.2% were female. Most patients received ICIs in the palliative setting (80.5%) and had good performance status, with ECOG 0-1 in 89.8%. Melanoma was the most frequent primary tumor (27.9%), followed by lung cancer (26.7%). Pembrolizumab was the most frequently used ICI (44.5%). Adverse events of any grade occurred in 54.2% of patients, of which 40.7% were immune-related. Among patients with immune-related adverse events, the most frequent categories were endocrine toxicities (26.0%) and cutaneous toxicities (22.9%). The median cycle at irAE onset was 3 (IQR 2–7). Grade 3-4 adverse events were observed in 12.7% of patients. Overall, systemic corticosteroids were required in 18.6% of patients, and treatment interruption or discontinuation due to toxicity occurred in 18.2% of patients. Conclusions: In this real-world single-center cohort, irAEs associated with ICIs were common and clinically relevant, frequently requiring systemic corticosteroids and leading to treatment interruption or discontinuation in a substantial proportion of patients. These findings emphasize the importance of early recognition and structured management of irAEs in routine oncology practice.