Kinetic analysis of the growth rate of sporadic and hereditary medullary thyroid carcinoma: Comparing the postoperative calcitonin-doubling rate with the hypothetical preoperative tumor volume-doubling rate

Background Our previous kinetic analyses of changes in the tumor volume (TV) of papillary thyroid microcarcinomas during active surveillance revealed that the tumors' growth varied over time from rather rapid growth to shrinkage and that the hypothetical TV-doubling rates (DRs) before the patients' presentation were much larger than their observed TV-DRs, indicating that rapid growth phases preceded their presentation. Whether this phenomenon also occurs in medullary thyroid carcinoma (MTC) was unknown. Methods We retrospectively analyzed the cases of 46 MTC patients (18 hereditary, 28 sporadic; 9–80 years old at surgery, median 53.5 years; 19 males and 27 females) with elevated postoperative calcitonin (Ct) suggesting persistent disease. We calculated each patient's Ct-DR and his/her hypothetical TV-DR, using the tumor size and age at surgery. Results Ct-DRs (/year) after surgery were >0.5, 0.1–0.5, −0.1–0.1, and <������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������