Relation of Doubling Time of Plasma Calcitonin Levels to Prognosis and Recurrence of Medullary Thyroid Carcinoma

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Abstract
Plasma calcitonin (CT) levels were measured serially in 54 patients surgically treated for medullary thyroid carcinoma. Patients with postoperative basal CT levels higher than 1 ng/ml measured within 1 month after surgery had a higher recurrence rate than those with lower CT levels (p < 0.002). Patients with postoperative basal CT levels higher than 2 ng/ml had a lower survival rate than those with lower CT levels (p < 0.01). However, pre-operative basal CT levels had no significant correlation with life expectancy or recurrence during the present observation period. Serial measurements in 23 patients with elevated postoperative CT levels showed exponential increases in basal CT levels in 19 patients (p < 0.05 in nine patients, 0.05 < p < 0.1 in four patients) and slight decreases in four (p < 0.05 in one patient). Doubling time of CT levels calculated from the regression line in each patient showed the highest correlation with 3-year survival, recurrence within 5 years, and time interval between surgery and clinical recurrence of the tumor, allowing quantitative prediction of the prognosis.