Age matters: Real-world evidence of increased immunotherapy toxicity in elderly patients from a Brazilian oncology hospital.

e23258 Background: Immunotherapy with immune checkpoint inhibitors (ICI) is widely used in cancer treatment. While effective, ICIs can cause immune-mediated adverse events (irAEs), particularly in elderly patients who may be more vulnerable due to age-related factors. However, the association between age and severe irAEs remains controversial, especially in real-world settings. This study aimed to evaluate age as a predictor of severe irAEs and treatment discontinuation in patients receiving ICIs. Methods: This retrospective single-center study was conducted at Instituto Brasileiro de Controle do Câncer (IBCC), São Paulo, Brazil, and included patients treated with anti-PD1/PDL1 agents, either as monotherapy or in combination with chemotherapy, from January 1, 2018, to June 30, 2023. Patients treated with anti-CTLA-4 monotherapy were excluded. Patients aged over 65 years were classified as elderly. The primary aim was to evaluate age as a risk factor for severe immune-mediated adverse events (common terminology criteria for adverse events - CTCAE - grades three or four). The secondary aim was to evaluate age as a risk factor for corticosteroid use and treatment discontinuation. Multiple logistic regression was performed to assess the association between age and the outcomes. The analysis included performance status and use of immunotherapy in combination or as monotherapy as potential confounders. Results: A total of 168 patients were included (mean age 61 years, range 17–92; 52.3% female). Lung cancer (31.4%), melanoma (24.3%), and breast cancer (8.3%) were the most common tumor types. Elderly patients (47.6%) had a significantly higher risk of grade 3-4 irAEs (28.7% vs. 11.4%; OR = 5.36, 95% CI 1.59–18.10, p = 0.007) and treatment discontinuation (20.0% vs. 8.0%; OR = 2.74, 95% CI 1.14–6.6, p = 0.024) compared to younger patients. No significant association was found between age and corticosteroid use (OR = 2.15, 95% CI 0.90–5.13, p = 0.085). Conclusions: In this real-world analysis from a Brazilian oncology hospital, patients aged over 65 years were at higher risk of severe irAEs and treatment discontinuation with ICIs. These findings highlight the importance of individualized treatment strategies and vigilant monitoring in elderly patients receiving ICIs.