Refractory hypercalcemia of malignancy related to vitamin D toxicity: Treatment strategies

Introduction: Hypercalcemia of malignancy (HCM) is a known cancer complication resulting in morbidity and mortality. It is most often mediated by parathyroid hormone related peptide (PTHrP) or direct bone invasion, but may be related to other humoral causes. Most cases of HCM respond to standard therapies such as fluids, loop diuretics, bisphosphonates, calcitonin, denosumab and control of the underlying malignancy. Case Report: This report describes the case of a 60-year-old woman with metastatic breast cancer and vitamin D toxicity who developed PTHrP driven HCM. The case is a unique example of breast cancer related HCM in the absence of bone metastases. The hypercalcemia was refractory to standard treatments including intravenous bisphosphonates, fluids and calcitonin. Ultimately, the patient responded to denosumab dosed every seven days along with daily intravenous hydration. Response was maintained despite failure to control the underlying malignancy. Conclusion: Vitamin D toxicity may exacerbate PTHrP driven HCM. Frequent dosing of denosumab is shown to Mohammed Athar Naeem1, JoAnn Roslyn Phillips2, Patrick Michael Dillon3 Affiliations: 1Oncology Fellow, University of Virginia, Charlottesville, VA, USA; 2Oncology Navigator, University of Virginia, Charlottesville, VA, USA; 3Associate Professor of Oncology, University of Virginia, Charlottesville, VA, USA. Corresponding Author: Patrick Dillon, MD Associate Professor, UVA Division of Hematology/Oncology, UVA Box 800716, Charlottesville, VA 22908, United States; E-mail: [email protected] Received: 13 July 2016 Accepted: 13 September 2016 Published: 05 October 2016 PEER REVIEWED | OPEN A CE S be safe and effective in refractory HCM. The mechanisms and management of vitamin D toxicity are reviewed.