[Prognostic values of the doubling time of serum carcinoembryonic antigen and calcitonin levels in medullary thyroid carcinoma].

Fifteen patients operated on for medullary thyroid carcinoma with elevated postoperative serum calcitonin (CT) levels underwent serial measurements of serum CT and carcinoembryonic antigen (CEA) levels. Both CT and CEA levels showed an exponential increase in 12 patients and a slight decrease in three. CEA levels manifested less fluctuation than CT levels. The doubling time of these tumor marker levels calculated from the regression line in each patient showed a strong correlation with three-year survival, recurrence within five years, and the time interval between surgery and recurrence of the tumor, allowing quantitative prediction of the prognosis. However, the doubling time of CEA was longer than that of CT in most patients.