e16004 Background: We report a case of inoperable metastatic parathyroid carcinoma with life-threatening hypercalcaemia. We achieved rapid control of calcium with denosumab. Methods: Our patient presented with complications of hyperparathyroidism. He underwent a partial parathyroidectomy and hemithyroidectomy. Parathyroid carcinoma was confirmed. There was no metastatic disease. A year later he was hypercalcaemic, 4.15 mmol/L (2.15-2.60 mmol/L), with elevated PTH and creatinine. FDG activity was seen on PET at the thyroid bed and retrocrural space. Extensive pleural metastases limited resection to debulking. The calcium and PTH remained elevated. Hydration and zoledronic acid had little effect. Cinacalcet 90mg QDS led to no improvement in calcium. Weekly zoledronic acid was used to keep his calcium below 4 mmol/L. Two cycles of cyclophosphamide, 5-flurouracil and dacarbazine led to no decline in the calcium. Denosumab is a fully human monoclonal IgG2 antibody with a high affinity and specificity to bind RANK ligand, mimicking Osteoprotegerin, competitively blocking the binding of RANK to its ligand to inhibit osteoclast activation. Results: 120mg was given subcutaneously. By day 8 the calcium had dropped to 2.66 mmol/L. After a second dose, the calcium was 2.33 mmol/L. Bone turnover markers were rapidly suppressed. The calcium was in the normal range for four months with improved renal function. Further denosumab will be guided by serum calcium. Conclusions: Parathyroid carcinoma is rare. The mainstay of treatment is resection, even in metastatic disease. Often the disease is refractory to medical management leading to complications of hypercalcaemia. There is limited evidence for chemotherapy and few strategies to manage resistant hypercalcaemia have been published. In this case refractory hypercalcaemia dramatically responded to denosumab. Denosumab does not require dose adjustment for renal impairment, a common finding with hypercalcaemia. In this case denosumab offered prolonged control of serum calcium. We propose that denosumab should be considered for patients with hypercalcaemia due to parathyroid cancer.
Parathyroid Carcinoma Case Report: Rapid Control of Refractory Hypercalcemia with Denosumab
