Pharmacotherapy
Some Cancer Patients Treated With Cetuximab May Require Magnesium Supplementation
By Journal of the National Cancer Institute
Aug 19, 2005 - 4:59:00 AM

Some cancer patients being treated with cetuximab (Erbitux) may develop abnormally low blood levels of magnesium (hypomagnesemia) and require supplementation, according to a new study.

Cetuximab--a monoclonal antibody against the epidermal growth factor receptor (EGFR)--is used to treat patients with metastatic colorectal cancer and is being evaluated for the treatment of several other solid tumors. After treating a 34-year-old male colorectal cancer patient who developed profound fatigue and hypomagnesemia while on cetuximab therapy, Deborah Schrag, M.D., of Memorial Sloan-Kettering Cancer Center in New York, and colleagues reviewed the incidence of electrolyte abnormalities among a consecutive case series of 154 patients treated with cetuximab at their institution.

Of the 34 patients who had their magnesium levels measured at least once during cetuximab treatment, six had grade 3 hypomagnesemia and two had grade 4. The authors hypothesize that because EGFR is strongly expressed in the kidney--particularly where most of the magnesium is reabsorbed into the organ--blocking EGFR with cetuximab may interfere with magnesium transport. They suggest that if cetuximab-treated patients have symptoms of hypomagnesemia--fatigue, paresthesias (itching, burning, or tingling skin sensations), and low levels of calcium in the blood--then they should have their magnesium levels checked and, if low, receive magnesium supplementation.

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