PROGRESSION OF POSTOPERATIVE RESIDUAL MEDULLARY-THYROID CARCINOMA AS MONITORED BY PLASMA CALCITONIN LEVELS

Background. Patients operated on for medullary thyroid carcinoma (MTC) frequently have persistent elevated plasma calcitonin concentrations after operation, indicating remaining tumor: The plasma calcitonin con centration in a patient with MTC roughly reflects the endogenous tumor burden. The only effective treatment for MTC is surgical. The decisio n about whether a patient with persistent MTC should have a repeat ope ration would be influenced by knowledge of the natural course of the d isease. Methods. Forty patients with persistently elevated peak plasma calcitonin concentrations after thyroidectomy for MTC were monitored for a mean of 6 years. Serial determinations of plasma calcitonin leve ls were obtained before and after intravenous injection of calcium and pentagastrin. Results. At the first postoperative test 63 % of the pa tients had undetectable basal calcitonin values, although their stimul ated plasma calcitonin concentrations were elevated. The mean annual i ncrease in stimulated plasma calcitonin concentrations was 117 %, but plasma calcitonin concentrations were stable in three patients and dec reased in one patient I;ive patients are known to have experienced dis tant metastases. Conclusions, MTC is a progressive disease in most pat ients with persistent hypercalcitoninemia after thyroidectomy. Stimula ted peak plasma calcitonin levels are more meaningful than basal level s in the serial postoperative evaluation of patients with persistent h ypercalcitoninemia after thyroidectomy for MTC.