Changes of Biochemical Factors and the Effect on Recurrence of Medullary Thyroid Carcinoma after Surgery

Objective Medullary thyroid carcinoma (MTC) is a rare malignancy secreting calcitonin (Ctn). we aimed to analyze the relationship between Ctn levels at different time points in patients with MTC, and evaluate its predictive effect on recurrence. Methods A retrospective study of patients diagnosed with MTC in a large medical center were conducted in northern China. The interrelationships between preoperative Ctn, normalization of postoperative serum Ctn at the first month (NPS), and long-term biochemical cure as well as their predicting roles on structural recurrence were assessed. Results A total of 212 patients were included in this study. The median follow-up time was 59.5 months. The 5- and 10-year cumulative disease-free survival rates were 81.5% and 66.8%, respectively. NPS (OR: 216.33, 95% CI: 28.69-1631.09, P<0.001) and absence of structural recurrence (OR: 61.71, 95% CI: 3.90-975.31; P=0.003) were associated with biochemical cure. Non-biochemical cure (OR: 28.76; 95% CI: 2.84-290.86; P=0.004, HR: 14.63, 95% CI: 2.27-94.07, P=0.005), larger tumor size (OR: 8.79, 95% CI: 2.12-36.40, P=0.003, HR: 5.41, 95% CI: 2.04-14.37, P=0.001), and multifocality (OR: 4.02, 95% CI: 1.06-15.17, P=0.040, HR: 3.00, 95% CI: 1.18-7.60, P=0.021) were unfavorable independent predictors of structural recurrence and disease-free survival. For sporadic MTC confined to the thyroid lobe, there was no difference in biochemical or structural prognosis between the different surgeries in the subgroup analysis. Conclusions NPS, rather than preoperative Ctn, predicted long-term biochemical cure for MTC. Non-biochemical cure, larger tumor burden including larger tumor size and multifocality at initial surgery, served as worse prognostic predictors.