Preoperative calcitonin testing improves the diagnosis of medullary thyroid carcinoma in female and male patients

Calcitonin (Ctn) measurement in patients with thyroid disease could potentially increase the detection rates of medullary thyroid carcinoma (MTC) but remains a controversial issue. The aim of this study was to evaluate routine preoperative Ctn measurements. Methods: All patients with thyroid surgery documented in the prospective StuDoQ|Thyroid registry between 03/2017 and 09/2020 were included. Cutoff levels for Ctn were determined with ROC analyses to assess the preoperative diagnosis of MTC in subgroups for females and males. Findings: In 29.590 of 39.679 patients (75%) participating in the registry, routine preoperative Ctn testing was performed. In 357 patients (227 females, 130 males) histopathology confirmed MTC with a mean tumor size of 14.7 mm (± 12.43). Biochemical cure was achieved in 71.4% of the patients. Ctn levels between 11 and 20 pg/ml were seen in 2.6% of the patients, and only 0.7% of the patients had Ctn levels above 21 pg/ml. Cutoff levels for the diagnosis of MTC were 7.9 pg/ml for females and 15 pg/ml for males (p <0.001). The sensitivity and specificity for females were 95% and 98%, and 96% and 97% for males, respectively. Conclusion: Routine Ctn testing is a reliable predictor for MTC and provides the opportunity for earlier thyroidectomy before lymph node metastases occur, resulting in a better prognosis. Females with Ctn levels >7.9 pg/ml and males >15 pg/ml without any other extrathyroidal sources for an elevated Ctn should be monitored. Thyroid surgery should be considered if Ctn levels are increasing, or ultrasound detects suspicious thyroid lesions.