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Osimertinib Stomatitis — SCE Medical Oncology MCQ

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ModerateImmunotherapy & Targeted TherapyOsimertinib StomatitisSCE Medical Oncology

A patient on osimertinib for EGFR-mutant NSCLC develops grade 2 stomatitis (painful oral ulcers). This was not a common toxicity with first-generation EGFR TKIs. What explains this?

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Correct answer: C — Osimertinib's broader kinase inhibition profile (including inhibition of HER2/HER4 in addition to EGFR) contributes to mucosal toxicity — management includes dose reduction, topical agents and oral hygiene

Osimertinib inhibits wild-type EGFR and mutant EGFR more broadly than first-generation TKIs, with additional activity against HER2 and HER4. This wider kinase inhibition contributes to mucosal toxicity (stomatitis, diarrhoea) not commonly seen with gefitinib/erlotinib. Management includes dose reduction (80→40 mg), topical agents (benzydamine mouthwash, steroid pastes), and good oral hygiene. Grade 3 stomatitis requires osimertinib hold until resolution.

Reference: BNF Osimertinib; ESMO 2024 NSCLC; Soria et al NEJM 2018 FLAURA safety data