Anti-
epidermal growth factor receptor (EGFR) antibody is widely used for the treatment of patients with metastatic
colorectal cancer. Hypomagnesemia is a comparatively frequent adverse event of this
drug, which is likely overlooked because it occurs later in treatment without symptoms. Furthermore, hypomagnesemia and hypomagnesemia-induced corrected QT (QTc) prolongation may lead to
loss of consciousness (LOC), the onset of which is not generally considered associated with the treatment of anti-EGFR antibody because of its rare occurrence. Here, we present a
colorectal cancer patient treated with anti-EGFR antibody, who suffered LOC during treatment while severe hypomagnesemia or QTc prolongation was not observed.
CASE PRESENTATION: A 69-year-old man with metastatic
colon cancer was treated with
cetuximab (anti-EGFR antibody) plus
irinotecan as third-line
chemotherapy. His serum
magnesium level gradually decreased, and grade 2 hypomagnesemia (a serum
magnesium level of 0.9 mg/dL) was observed at the 12th administration of
cetuximab. In light of this development, intravenous supplementation of 20 mEq
magnesium sulfate began with careful blood monitoring despite the lack of clinical symptoms. Electrocardiogram (ECG) showed prolonged QT or corrected QT (QTc) intervals (grade 1). His serum
magnesium level remained at 0.9 mg/dL, and no hypomagnesemia symptoms were observed by the 17th administration of
cetuximab. After the treatment, however, he suddenly lost consciousness without symptoms related to infusion or
allergic reactions.
Circulatory collapse following dermatological reactions and respiratory events were not evident. Intravenous supplementation of
magnesium sulfate was administered again. He awakened 2 min after the onset of temporary LOC without any other symptoms related to hypomagnesemia, such as
lethargy,
tremor,
tetany, and
seizures. No other etiology outside of the low level of serum
magnesium was confirmed in further examinations.
Cetuximab was discontinued, and his serum
magnesium level returned to a level within the normal range after 6 weeks. Because of
tumor progression,
regorafenib and
TAS-102 (
trifluridine tipiracil hydrochloride) were introduced sequentially for 6 months. Five months after the final treatment of
TAS-102, he died of his primary disease, which reflected a survival period of 4 years and 6 months since the beginning of treatment.
CONCLUSIONS: This case report reminds clinicians that LOC can be induced without severe hypomagnesemia or QTc prolongation, during anti-EGFR antibody treatment for metastatic
colorectal cancer even while under carefully monitored
magnesium supplementation.