OBJECTIVE To investigate the diagnostic efficacy of serum calcitonin(Ctn)in medullary thyroid cancer(MTC),the correlation between preoperative serum Ctn and clinicopathological features,and the risk factors affecting the progression of MTC disease during follow-up.METHODS The clinical data of 50 patients admitted to the Hospital of Integrated Traditional Chinese and Western Medicine of Nanjing University of Chinese Medicine from 2011 to 2022 were systematically reviewed,the ROC curve calculated the diagnostic efficacy of Ctn and CEA levels on MTC,and the risk factors for lymph node metastasis in the central region of MTC were analyzed in univariate and multivariate,and the survival curve without disease progression was drawn to predict risk factors.RESULTS The ROC curve yields the preoperative cut-off value of Ctn was 23.81 pg/ml and the cut-off value of CEA was 3.035 ng/ml for the diagnosis of MTC.The age of disease,tumor diameter,and preoperative serum Ctn and CEA levels in MTC patients were higher than those in non-MTC patients.Ctn≥289.62 pg/ml was an independent risk factor for central lymph node metastasis in MTC.The survival curve showed that invasion of the capsule,central region metastasis,and TNM stage above T2 were risk factors for predicting disease progression(P<0.05).Patients with MTC who have disease progression have higher preoperative Ctn.CONCLUSION Serum Ctn has important clinical value in the differential diagnosis,preoperative evaluation and postoperative follow-up of MTC.