Background: All patients with medullary carcinoma of the thyroid (MCT) diagnosed in Sweden during 1959 through 1981 were identified. There were 113 males and 134 females with a mean age of 51.6 years (range, 11-85 years). The cohort was followed with regard to survival to identify prognostic factors. The results 5 and 10 years after diagnosis have been presented previously.
Methods: The purpose of this study was to examine to what extent those prognostic factors found in the authors' previous analyses remained independent prognostic factors for survival 10 years or longer after diagnosis. The follow-up period was extended an additional 5 years and ranged between 11 and 32 years.
Results: The relative survival rate was 69.2% and 64.7%, respectively, 10 and 15 years after diagnosis. The survival rate was worse after excluding those patients with a family history of MCT (60.8% and 53.7%, respectively, 10 and 15 years after diagnosis). In multivariate analyses, age, tumor size, stage of the disease at diagnosis, tumor amyloid content and an euploid DNA pattern were found to be independent prognostic factors. However, in analyses of survival 10 years or longer after diagnosis only stage, tumor size, and age remained independent prognostic factors.
Conclusions: There is still an excess mortality 10 years or longer after a diagnosis of MCT. However, the authors identified 3 groups of patients in whom the survival 10 years or longer after diagnosis did not differ from that of the general population: patients with a family history of MCT detected by screening, those with tumor size < 1 cm, or those with early stage disease at diagnosis.