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Anti-EGFR Hypomagnesaemia — SCE Medical Oncology MCQ

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ModerateGI CancersAnti-EGFR HypomagnesaemiaSCE Medical Oncology

A 58-year-old woman with metastatic CRC on cetuximab develops severe hypomagnesaemia (Mg 0.4 mmol/L). She has muscle cramps and paraesthesia. What is the mechanism?

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Correct answer: E — EGFR inhibition in the renal distal convoluted tubule reduces expression of the TRPM6 magnesium channel, causing renal magnesium wasting — this is a class effect of anti-EGFR antibodies requiring regular monitoring and IV supplementation

Anti-EGFR antibodies (cetuximab, panitumumab) cause renal magnesium wasting by inhibiting EGFR-dependent TRPM6 channel expression in the distal convoluted tubule. Hypomagnesaemia occurs in approximately 10-30% of patients and can be severe. Oral magnesium supplementation is often insufficient; IV magnesium replacement may be required. Regular serum magnesium monitoring (at least every 2 weeks during treatment) is mandatory. Secondary hypocalcaemia and hypokalaemia can occur if hypomagnesaemia is untreated.

Reference: BNF Cetuximab; ESMO Supportive Care; Groenestege et al JCI 2007