Medullary thyroid carcinoma surgical cytoreduction induces an increase in serum calcitonin and carcinoembryonic antigen doubling times.

Serum calcitonin (Ct) and carcinoembryonic antigen (CEA) doubling times (DT) are considered to be strong prognostic markers in patients with medullary thyroid carcinoma (MTC). The Objective of this work is to study the effect of MTC debulking on Ct and CEA DTs. 4 patients with MTC are presented who after an initial neck operation had residual disease were followed-up with serial measurements of serum Ct and CEA for several years before and after a secondary incomplete removal of involved cervical lymph nodes. The patients received no other treatment for MTC. Ct and CEA DTs were determined after fitting the Ct or CEA values to an exponential growth equation. In patient A, Ct DT increased from 1.45 years (1.17-1.89, 95% CI) preoperatively, to 5.72 (3.22-25.77) postoperatively. In patient B, Ct DT was 1.63 years (1.36-2.02) preoperatively, and very long (serum Ct practically ceased increasing) postoperatively. In patient C, Ct DT was 4.03 years (2.22-21.58) before, and very long after the operation. In patient D, Ct DT from 1.16 years (0.82-1.99) before, increased to 4.21 years (3.04-6.86) after the operation. The changes in CEA DTs were similar to those of Ct DTs in 2 patients in whom the tumor was apparently producing the protein. In conclusion, surgical MTC cytoreduction in 4 patients caused an increase in the Ct and CEA DTs, and the patients could be reclassified in new Ct DT-based strata with better prognosis than before the operation. We hypothesize that such tumor burden reduction may slow the growth of any residual MTC and we discuss mechanisms that could be responsible for this phenomenon.