Cancer-Associated Hypercalcemia

A 60-year-old woman presents to the emergency department with somnolence and poor appetite. Five months earlier, she received a diagnosis of invasive, high-grade, urothelial carcinoma and underwent four cycles of neoadjuvant chemotherapy, and 1 month earlier, she underwent open radical cystectomy. She has no other significant medical history. The serum calcium level is 16.1 mg per deciliter (4.02 mmol per liter; reference range, 8.8 to 10.2 mg per deciliter [2.2 to 2.5 mmol per liter]); previous serum calcium levels were normal. The albumin level is 4 g per deciliter, blood urea nitrogen 27 mg per deciliter (9.6 mmol per liter), creatinine 1.2 mg per deciliter (106.1 mu mol per liter), and phosphorus 2.1 mg per deciliter (0.7 mmol per liter). The parathyroid hormone (PTH) level is 10 pg per milliliter (reference range, 15 to 65), parathyroid hormone-related protein (PTHrP) 187 pg per milliliter (reference range, 14 to 27), 25-hydroxyvitamin D 28 ng per milliliter (70 nmol per liter; reference range, 20 to 50 ng per milliliter [50 to 125 nmol per liter]), and 1,25-dihydroxyvitamin D 77 pg per milliliter (200 nmol per liter; reference range, 25 to 66 pg per milliliter [65 to 172 nmol per liter]). A whole-body bone scan shows no skeletal metastases. How should this patient be treated?