Denosumab has been demonstrated to be superior to Zoledronic acid for prevention of skeletal related events in patients with bone metastases from solid tumours.1 The safety profiles of both agents are comparable however hypocalcaemia is more frequent with Denosumab.2
We describe two patients with metastatic prostate cancer who required treatment for severe, symptomatic hypocalcaemia following Denosumab.
A 76 year old man from a nursing home presented with confusion, agitation, fever and acute kidney injury. He was found to have severe hypocalcaemia (corrected total plasma calcium 1.64mmol/L). His plasma calcium level eventually normalised with a combination of aggressive intravenous and oral calcium replacement, calcitriol and thiazide diuretic therapy.
A 74 year old man presented with lethargy and anorexia. Serum biochemistry revealed hypocalcaemia (corrected total plasma calcium 1.86mmol/L), hypophosphataemia, hypokalaemia and hypomagnesaemia. Medical history was notable for excessive alcohol intake, and poor nutritional status was thought to be a major contributor to his electrolyte abnormalities. He was commenced on oral potassium, phosphate and magnesium replacement and an increased dose of calcium carbonate and vitamin D. Three days later his hypocalcaemia worsened (corrected plasma calcium 1.29mmol/L). He required a continuous intravenous calcium infusion for over a week, magnesium infusion and high doses of calcitriol to eventually normalise his plasma calcium level.
Hypocalcaemia is an increasingly recognised adverse effect of Denosumab.2 While most cases are mild, severe and fatal cases have been reported.3 We discuss risk factors for the development of hypocalcaemia and review recommendations for the prevention and management of hypocalcaemia secondary to Denosumab.