Cetuximab-induced hypomagnesemia in patients with colorectal cancer.

Cetuximab treatment has been associated with severe hypomagnesemia, but the predisposing factors and management of this toxicity have been poorly characterized. 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 >or=1 repeat magnesium level during cetuximab treatment. The incidence, grade, and management of hypomagnesemia were described in the evaluable population. Among the evaluable population, 13 patients developed grade 3/4 hypomagnesemia (27%). The incidence of grade 3/4 hypomagnesemia was 6%, 23%, and 47% 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. 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.