97% of patients with cancer treated with monoclonal antibodies—cetuximab, matuzumab, or panitumumab—that target the epidermal growth factor receptor (EGFR) have some degree of magnesium loss (hypomagnesaemia), according to a study published in the May issue of The Lancet Oncology.
“Our study is important because it shows that magnesium wasting will occur in all patients…[Previously,] hypomagnesaemia was thought to be restricted to an undefined subset of patients”, says lead author Prof Sabine Tejpar. “Predicting the risk of hypomagnesaemia will also be important in those patients receiving combination treatments with nephrotoxic and potential magnesium-wasting agents, such as cisplatin.”
Previous retrospective studies had shown severe magnesium loss (grades 3 and 4 hypomagnesaemia) in only a small proportion of patients given anti-EGFR drugs and whether all or a subset of patients are affected was unknown. Hypomagnesaemia is a serious side-effect of treatment as it can cause dizziness, weakness, cardiac abnormalities, or even generalised convulsions. Furthermore, agents against EGFR are being used increasingly to treat solid tumours, in particular cancers of the colorectum. However, the extent of this side-effect in patients given these antibodies has not previously been fully assessed.
Prof Sabine Tejpar and colleagues therefore studied prospectively the degree of hypomagnesaemia in 98 patients with metastatic colorectal cancer treated with these antibodies. 95 (97%) of patients had decreased serum magnesium concentrations during treatment with the EGFR-targeted antibodies compared with baseline measures (mean serum magnesium slope –0.00157 mmol/L/day [95% CI –0.00191 to –0.00123]) and this change was significantly lower than that seen in the control group not receiving antibody treatment—ie, given chemotherapy alone (0.00014 mmol/L/day [–0.00026 to 0.00055]).