Clinical outcomes of patients with hypercalcitoninemia after initial treatment for medullary thyroid cancer and postoperative serum calcitonin cutoffs for predicting structural recurrence

Background: Persistent hypercalcitoninemia is reported in 40% to 60% of patients with medullary thyroid cancer (MTC) after initial therapy, but their clinical outcomes have not been clearly studied. We evaluated the outcomes of MTC with hypercalcitoninemia and assessed the cutoffs of postoperative serum calcitonin for predicting structural recurrence. Methods: A dynamic risk assessment system was used to categorize clinical outcomes in this retrospective study. Receiver operating characteristic (ROC) curve analysis was used to calculate the calcitonin cutoffs for predicting structural recurrence. Results: Among 120 patients operated on, 30 (25%) had persistent hypercalcitoninemia. Of that group, 18 (60%) had biochemical persistent disease and 11 (37%) developed structural identified disease, including 1 death (3%). Postoperative calcitonin <29 pg/mL predicted structural disease with 100% sensitivity, 90.5% specificity, and 100% negative predictive value. Conclusion: One third of the patients with MTC with hypercalcitoninemia experienced structural recurrence, and postoperative basal serum calcitonin might be a simple tumor marker to predict structural recurrence.