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irAEs — SCE Medical Oncology MCQ

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HardImmunotherapy & Targeted TherapyirAEsSCE Medical Oncology

A patient taking osimertinib 80 mg daily has QTc 506 ms and 512 ms on two ECGs, compared with 448 ms before treatment. Potassium and magnesium are corrected and there is no ventricular arrhythmia. What dose action is specified in the UK product information?

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Correct answer: A — Withhold; after QTc falls below 481 ms, restart osimertinib at 40 mg daily

The SmPC threshold is QTc above 500 ms on at least two ECGs. Osimertinib is withheld until QTc is below 481 ms, or has returned to baseline when baseline was at least 481 ms, and is then restarted at the reduced 40 mg dose. Permanent discontinuation is reserved for QT prolongation with serious arrhythmia or features such as torsade de pointes; continuing 80 mg or restarting it unchanged does not follow the dose table.

Reference: TAGRISSO 40 mg UK summary of product characteristics (Current UK SmPC, accessed August 2026): https://www.medicines.org.uk/emc/product/1985/smpc