Prognostic factors of sporadic or inherited medullary thyroid carcinoma (MTC) are still controversial and have been assessed in old and small series. A better knowledge of these factors would improve patient management.

To evaluate factors involved in the prognosis of MTC in a large series of cases, using uni‐ and multivariate analysis.

Clinical, biological, surgical and epidemiological data on 899 MTC patients, diagnosed between 1952 and 1996, were collected by the French Calcitonin Tumors Study Group (GETC) with a standardized questionnaire, and processed in a national database.

Survival and biochemical cure (i.e. normal basal post‐operative serum calcitonin levels) were analysed with Kaplan and Meier and log‐rank test statistical procedures. Data are presented as adjusted rather than observed survival, to consider only patients who died of MTC. Cox's forward‐stepping proportional hazard model was used to analyse factors with a significant influence on survival by univariate analysis.

Apart from the large proportion of familial forms (43%), the general characteristics of our population were similar to those in other studies: mean age at surgery = 43.4 years; sex ratio = 1 male/1.35 female; stage I = 20.8%; stage II = 21.2%; stage III = 46.5% and stage IV = 11.5%. 863 (96%) patients underwent surgery; 43% of operated patients were biochemically cured. Adjusted survival was 85.7 ± 1.5% at 5 years and 78.4 ± 2.1% at 10 years. Multivariate analysis showed that age and stage were independent predictive factors of survival. Gender, type of surgery, type of familial form were predictive only in univariate analysis. Biochemical cure predicts a survival rate of 97.7% at 10 years. Authentic recurrence, that is subsequent elevation of calcitonin (CT) after post‐operative normalization, was found in 4.9%. In non‐cured patients (57%), survival was still good: 80.2% (±2.2%) and 70.3% (±2.9%) at 5 and 10 years, respectively. Similarly, prediction of biochemical cure was solely dependent on stage.

Survival of these medullary thyroid carcinoma patients appears better than expected even in non‐cured patients. Considering the strong impact of stage, the necessity for pre‐operative diagnosis of MTC is obvious.