Background: 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.
Objective: To evaluate factors involved in the prognosis of MTC in a large series of cases, using uni- and multivariate analysis.
Design and patients: 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.
Measurements: 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.
Results: 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.
Conclusion: 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.