Osimertinib Adverse Effects — RACP Adult Medicine MCQ

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ModerateMedical OncologyOsimertinib Adverse EffectsRACP Adult Medicine

A 58-year-old man with metastatic non-small cell lung cancer (EGFR exon 19 deletion positive) is commenced on first-line osimertinib. What is the most common clinically significant adverse effect?

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Correct answer: E — Interstitial lung disease

While rash and diarrhoea are common (usually mild), the most clinically significant adverse effect of osimertinib is interstitial lung disease (ILD)/pneumonitis, occurring in ~3–4% of patients. It can be fatal. Patients presenting with new or worsening respiratory symptoms on osimertinib should have ILD excluded with HRCT before continuing therapy. QTc prolongation also occurs and requires ECG monitoring. The FLAURA trial established osimertinib as first-line for EGFR-mutant NSCLC with superior OS.

Reference: Cancer Council Australia – 2021 – Lung Cancer OCP; AMH – 2025 – Osimertinib