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Background and Importance Immune checkpoint inhibitors (ICIs) have revolutionised cancer treatment. However, chronic toxicities that persist beyond treatment discontinuation remain under-explored and insufficiently characterised in real-world settings. Pembrolizumab, an anti-programmed cell death protein 1 antibody, may induce long-term immune-related adverse events (irAEs) that impact patient quality of life and imply long-term clinical management.Aim and Objectives Characterise the prevalence, type and management of chronic toxicities associated with pembrolizumab.Material and Methods Retrospective observational study including adult patients who discontinued pembrolizumab and remained alive ≥12 months afterwards (from 01/2014 to 12/2022). Chronic toxicity was defined as any adverse event persisting ≥12 weeks after discontinuation. Clinical data were retrieved from electronic medical records. Variables collected: demographic data, cancer type, pembrolizumab treatment duration, type and grade of chronic toxicity, management strategies and clinical outcomes. Results expressed as median and interquartile range (IQR).Results One hundred patients were included. Median age at treatment initiation 64.7 years (IQR 56.3–76.0) and median body mass index 24.8 kg/m 2 (IQR 22.0–28.1). Median treatment duration 9.3 months (IQR 3.7–24.7). Most patients were male (61%), and 9% had a pre-existing autoimmune disease. Pembrolizumab was mainly prescribed for lung cancer (59%) and melanoma (27%), with 14% other malignancies. At the time of pembrolizumab initiation, most patients had locally advanced or metastatic disease, with 75% presenting brain metastases.Pembrolizumab discontinuation was due to disease progression (39%), immune-related toxicity (30%), treatment completion (20%) or other reasons (11%).A total of 340 adverse events were recorded, of which 110 (32.4%) were chronic. Most frequent chronic toxicities: asthenia (n=25), endocrine (n=24), gastrointestinal (n=21), dermatological (n=16) and rheumatological (n=10). Less frequent chronic toxicities: pulmonary (n=5), renal (n=3), neurological (n=3), haematological (n=1) and other events (n=1). Median severity grade 2 (IQR 1–3). Chronic toxicities persisted for more than 6 months in 38.5% of cases.Management strategies included corticosteroids in 17% of chronic toxicities (89% low-dose, 11% high-dose) and other immunosuppressants in 2%.Conclusion and Relevance Chronic toxicities after pembrolizumab are common, often moderate, and may persist for months. Endocrine, gastrointestinal and rheumatological irAEs predominate, requiring long-term follow-up. Identifying their frequency and management is essential to optimise multidisciplinary care.Conflict of Interest No conflict of interest