Endocrine Abstracts

Introduction: Parathyroid carcinoma (PC) mediated hypercalcemia is often severe and more resistant to medical treatment. 18F-Fluorocholine PET/CT is a new technique used for determining the localization of parathyroid lesions. Denosumab, novel antiresorbtive agent, has been shown to have a useful role in hypercalcemia treatment. We report a male patient in long-term follow-up of PC who had refractory hypercalcemia due to pulmonary metastases revealed with 18-Fluorocholine PET/CT and who was successfully treated with denosumab.

Case: A 49-year-old man with recurrent PC initially presented in July 2007 with diffuse bone pain at lower extremities and hypercalcemia A neck ultrasound and CT scanning revealed a 3.9×3×3.5 cm solid lesion adjacent to the lower pole of the left thyroid lobe that was shown to represent a single hyperfunctioning parathyroid lesion on 99mTc-sestamibi (MIBI) parathyroid scintigraphy. The patient underwent a left parathyroidectomy along with en-bloc left thyroid lobectomy and left lateral lymph node dissection. Histological examination revealed parathyroid carcinoma. Due to postoperatively increased calcium and PTH levels, the patient was re-operated two times during the follow-up period for local recurrences. Afterwards, local radiotherapy was applied. One year later, laboratory investigations showed significantly raised calcium and PTH levels. Intravenous bisphosphonate as zolendronic acid 4 mg/28 days was started. For last 3 years, he did not take the medication due to social problems. He had admitted to our department with severe hypercalcemia 10 years later the initial operation at June 2017. He had hypercalcemia (16.8 mg/dl). He was screened for local recurrence or metastases. In 18F-FDG PET/CT diffuse nonhomogeneous hypermetabolism in medullary bones mostly associated with metabolic bone disesase was detected. His serum calcium levels were not decreased to <14 mg/dl levels with standard therapy such as aggressive saline rehydration, intravenous bisphosphonate, hemodialysis, oral cinacalcet. He had also acute pancreatitis in hospitalised period. For detection of local recurrence, 18-Fluorocholine PET/CT which revealed high uptake on pulmonary nodules was performed. Subcutaneous denosumab of 60 mg/28 days was given. After 3 doses of denosumab, total calcium was measured as 11.4 mg/dl.

Conclusion: As in this case, imaging with 18F-fluorocholine PET/CT is feasible in recurrent/metastatic parathyroid carcinoma. In our patient, 18F-fluorocholine PET/CT seems superior to FDG-PET/CT for detection of metastases. Denosumab is a good choice in treatment of hypercalcemia in patients who are resistant to other therapies such as hemodialysis, bisphosphonates and calcimimetics.