Asymptomatic Hypocalcemia Related to Denosumab Administration in Bone-Metastatic Patient Affected by Colorectal Cancer: A Case Report.

Background: Denosumab, a fully humanized monoclonal neutralizing antibody inhibiting the RANK/RANKL/OPG signaling pathway, is widely used for treating patients with bone metastases. However, its use in cancer patients with bone metastases is burdened by the risk of all grades of hypocalcemia, with the severe grade being rare. In the literature, several cases of severe symptomatic hypocalcemia have been reported, particularly in patients with breast and prostate cancers. In this report, we present a rare case of asymptomatic hypocalcemia in a 78 years-old patient with sigmoid cancer and bone metastases.

Case presentation: Hypocalcemia was detected two weeks after the first denosumab administration, during routine biochemical evaluation. The patient reported only a mild nonspecific paresthesia after medical questioning, without relevant clinical symptoms. Despite the severity of the hypocalcemia, serum calcium levels began to improve after a short period of low-dose calcium and calcitriol therapy, though complete stabilization and normalization occurred after several weeks.

Conclusion: This case highlights the importance to consider severe paucisymptomatic or asymptomatic hypocalcemia as a possible side effect in bone-metastatic patients treated with denosumab. It is advisable to monitor serum calcium levels even in the absence of typical hypocalcemia-related symptoms.