Medullary thyroid carcinoma (MTC) is an uncommon thyroid tumor and the clinical course is variable. Many prognostic factors for MTC have been studied, but the significance of some of these factors remains controversial. This study aimed to evaluate the prognosis of recurrent disease in patients suffering with MTC.

Fifty three patients who were operated for MTC from 1987 to 2006 in Seoul National University Hospital (SNUH) was retrospectively analyzed. Their medical records were reviewed for the demographic data, the laboratory data and the clinical course, the treatment and the long-term outcome. The median duration of follow-up was 66.5 months. Forty-two patients who were operated on primarily in this hospital were analyzed for their recurrence free survival.

The mean age atdiagnosis was 41.8 years. There were 28 femaleand 25 male patients. Eleven patients (22.9%) had multifocal disease. There were 32 sporadic MTC patients, 15 MEN2A patients, 3 familial medullary thyroid carcinoma (FMTC) patients and 1 MEN 2B patient. The 10- and 15-year overall survival rates were 91.9% and 76.5%, respectively; the 5- and 10-year recurrence-free survival rates were 70.6% and 45.5%, respectively. By univariate statistical analysis, the stage (stage I/II vs. III/IV, P=0.025), extrathyroidal extension (P=0.039), cervical lymph node metastasis (P=0.044), and the postoperative calcitonin level (≥25 pg/ml) (P=0.003) were the significant factors that influenced recurrence.

The overall prognosis of MTC is favorable. The significantfactors for a poor prognosis were the presence of lymph node metastasis, TNM stage III and IV, positive extrathyroidal extension at the first diagnosis and a high postoperative calcitonin level.