Updated Cutoff Values of Basal Serum Calcitonin to Discriminate True Medullary Thyroid Cancer from Other Conditions of Hypercalcitoninemia

Background: Calcitonin (Ctn) is a tumor marker of medullary thyroid carcinoma (MTC). However, serum Ctn cutoff values for MTC diagnosis are still under discussion. This study aimed to identify the cutoff values of Ctn and explore the relationship between two tumor markers (Ctn and carcinoembryonic antigen (CEA)) and disease burden. Methods This was a retrospective study conducted in West China Hospital of Sichuan University. We included 61 MTC patients and 235 non-MTC patients with nonspecific elevation of Ctn (> 9.52 pg/mL for males and > 6.40 pg/mL for females) and collected patients’ demographic information, essential serological indicators, cervical ultrasound and pathological reports. Results Unlike MTC, papillary thyroid carcinoma (40.85%), uremia (18.73%), chronic renal disease (10.21%) and inflammation (8.94%) commonly occurred with hypercalcitoninemia. The Ctn cutoff values were 38.24 pg/mL for males and 26.00 pg/mL for females. The Ctn level was found to be positively related to the largest tumor diameter (r = 0.702). Serum Ctn levels were significantly higher in patients with lymph node metastasis than in those without (P  0.05). Conclusion The best Ctn cutoff values for Chinese people to discriminate MTC from other hypercalcitoninemia conditions are 38.24 pg/mL for males and 26.00 pg/mL for females.