As checkpoint inhibitors such as pembrolizumab spread across tumour types, any clinician may meet their immune-related adverse events, which differ fundamentally from chemotherapy toxicity and can affect almost any organ.
Think of an immune-related adverse event in any patient on, or recently on, a checkpoint inhibitor who develops new symptoms: colitis with diarrhoea, hepatitis, pneumonitis with breathlessness or cough, endocrinopathies such as thyroid dysfunction, hypophysitis or new diabetes, and skin or less common neurological and cardiac effects. They can appear weeks to months after starting and even after stopping. The mainstay of treatment for moderate-to-severe events is prompt corticosteroids and holding the drug, guided by severity grading, and endocrine effects often need hormone replacement rather than steroids.
The habit worth keeping is to ask whether a new symptom in a patient on immunotherapy is immune-related before attributing it to infection or progression, because early recognition and steroids change the outcome.
- Suspect an immune-related adverse event with any new symptom on or after a checkpoint inhibitor.
- Common targets are gut, liver, lung, skin and endocrine organs; neurological and cardiac effects are rarer but serious.
- Events can appear months after starting and even after the drug is stopped.
- Treat moderate-to-severe events with prompt corticosteroids and by holding the drug.
- Endocrine effects usually need hormone replacement rather than steroids.
Why it matters
These toxicities are treatable when caught early but dangerous when mistaken for infection or disease progression.
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