Dynamic risk stratification for medullary thyroid cancer according to the response to initial therapy.

Detecting persistent/recurrent disease of medullary thyroid carcinoma (MTC) is important. The tumor-node-metastasis (TNM) staging system is useful for predicting disease-specific mortality, but is a static system and does not include postoperative serum calcitonin levels. We have focused on the clinical usefulness of dynamic risk stratification (DRS) using the best response to the initial therapy in MTC patients. A total of 120 MTC patients were classified into three DRS groups based on their responses to initial therapy. Clinical outcomes were assessed according to TNM staging and DRS. In the DRS, 70, 23 and 7 % of the MTC patients were classified into excellent, biochemical incomplete, or structural incomplete response groups, respectively. On TNM staging, 37, 16, 13 and 35 % of patients were stages I-IV, respectively. There were significant differences in survivals according to TNM staging (p = 0.03) and DRS (p = 0.005). During the median follow-up of 6.2 years, 75 patients (63 %) demonstrated no evidence of disease (NED). About 60 and 17 % of patients in stages III and IV were NED, respectively. DRS predicted NED better than TNM staging according to the proportion of variance explained (PVE) (49.1 vs. 28.7 %, respectively). At the final follow-up, 88, 4 and 0 % of patients in excellent, biochemical incomplete, and structural incomplete response groups attained NED, respectively. DRS based on the best response to the initial therapy can provide useful prognostic information in addition to initial TNM staging for predicting of mortality, as well as the likelihood of NED in MTC patients.