A Decrease of Calcitonin Serum Concentrations Less Than 50 Percent 30 Minutes after Thyroid Surgery Suggests Incomplete C-Cell Tumor Tissue Removal

Context and Objectives: The prognosis of medullary thyroid carcinoma (MTC) depends on the completeness of the first surgical treatment. To date, it is not possible to predict whether the tumor has been completely removed after surgery. The aim of this study was to evaluate the reliability of an intraoperative calcitonin monitoring as a predictor of the final outcome after surgery in patients with MTC. Patients and Methods: Twenty patients underwent total thyroidectomy and central lymph node dissection on the basis of a positive pentagastrin test. In six cases a preoperative diagnosis of MTC was achieved at the cytological examination. During the surgical intervention, calcitonin was measured at the time of anesthesia, at the time of manipulation, and 10 and 30 min after surgical excision. At the histological examination, 10 patients had MTC and 10 had C cell hyperplasia. Results: As compared with calcitonin levels before thyroidectomy, a decrease of calcitonin greater than 50% 30 min after surgery was able to significantly distinguish patients who were cured from those who experienced persistence of disease. It was not possible to find a similar result when the decrease of calcitonin 10 min after surgery was considered. Conclusions: A rate of calcitonin decrease less than 50% 30 min after thyroidectomy plus central neck lymph node dissection suggests the persistence of tumor tissue in patients operated for MTC. These results indicate that intraoperative calcitonin monitoring may be a useful tool to predict the completeness of surgery in patients with MTC. A rate of calcitonin decrease