Cetuximab-induced hypomagnesemia in patients with colorectal cancer

Background: Cetuximab treatment has been associated with severe hypomagnesemia, but the predisposing factors and management of this toxicity have been poorly characterized. Patients and Methods: The charts of 114 patients with colorectal cancer treated with cetuximab were reviewed. Forty-eight evaluable patients had normal magnesium levels before initiation of cetuximab and ≥ 1 repeat magnesium level during cetuximab treatment. The incidence, grade, and management of hypomagnesemia were described in the evaluable population. Results: Among the evaluable population, 13 patients developed grade 3/4 hypomagnesemia (27%). The incidence of grade 3/4 hypomagnesemia was 6%, 23%, and in patients receiving < 3 months, 3-6 months, and > 6 months of cetuximab therapy, respectively. Grade 3/4 hypomagnesemia was refractory to oral supplementation and required daily to 3-times-weekly intravenous magnesium sulfate supplementation at 6-10 g per dose. Recovery or amelioration in hypomagnesemia occurred approximately 4 weeks after cetuximab discontinuation. Conclusion: Severe hypomagnesemia is a frequent side effect of cetuximab therapy. Treatment of hypomagnesemia requires frequent intravenous magnesium supplementation and can be associated with significant patient inconvenience and an increased risk of venous access-related complications. Intermittent cetuximab schedules need to be investigated in order to reduce the frequency and severity of hypomagnesemia.