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Anti-EGFR Hypersensitivity — SCE Medical Oncology MCQ

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EasyGI CancersAnti-EGFR HypersensitivitySCE Medical Oncology

A 55-year-old man with metastatic colorectal cancer develops a rash during cetuximab infusion. He tolerates panitumumab without difficulty. Why might panitumumab be tolerated when cetuximab caused hypersensitivity?

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Correct answer: C — Cetuximab is a chimeric (mouse/human) IgG1 antibody more likely to cause infusion reactions, while panitumumab is a fully human IgG2 antibody with lower immunogenicity

Cetuximab (chimeric mouse/human IgG1) has higher immunogenicity than panitumumab (fully human IgG2), leading to more frequent infusion reactions (~15-20% vs ~1-3%). Severe cetuximab hypersensitivity is associated with pre-existing IgE antibodies to galactose-alpha-1,3-galactose (alpha-gal, linked to tick bites). Panitumumab can often be safely administered after cetuximab hypersensitivity because it lacks the immunogenic murine component and has a different IgG subclass.

Reference: BNF Cetuximab/Panitumumab; ESMO 2024 mCRC Guidelines