CONTEXT The increase in thyroid screening in the general population may lead to earlier detection of medullary thyroid carcinoma (MTC).

OBJECTIVE We aimed to evaluate secular trends in clinicopathological characteristics and long-term prognosis of MTC and its prognostic factors.

DESIGN This was a retrospective analysis from 1982 to 2012.

PATIENTS Three hundred and thirty-one patients with MTC were included and grouped based on the year of diagnosis (1982-2000, 2001-2005, 2006-2010 and 2011-2012).

MEASUREMENTS These included recurrence and mortality as well as biochemical remission (BCR) of serum calcitonin.

RESULTS Mean tumour size (from 2·5 cm to 1·7 cm, P < 0·001) and percentage of extrathyroidal extension (from 52·0% to 26·0%, P = 0·026) decreased. The percentage of patients achieving BCR within six postoperative months (po-BCR) increased with time (from 39·6% to 76·1%, P < 0·001). The 5-year overall recurrence rate significantly decreased in 2006-2012 compared to 1982-2005 (10% vs 18%, respectively, P = 0·031), although the 5-year survival rate did not improve (92% vs 92%, P = 0·929). Failure to achieve po-BCR was the strongest predictive factor associated with recurrence (hazard ratio [HR] = 58·04, 95% CI 7·14-472·11; P < 0·001). Male gender (HR = 3·18, 95% CI 1·18-8·56; P = 0·022), tumour size >2 cm (HR = 18·33, 95% CI 2·35-143·06; P = 0·006) and distant metastasis (HR = 4·00, 95% CI 1·31-12·21; P = 0·015) were significant prognostic factors for mortality.

CONCLUSIONS Clinicopathological characteristics and recurrence of MTC improved with time. Po-BCR was the best predictive factor for recurrence-free survival.