Calcitonin level in the postoperative period as a risk factor for persistence of medular thyroid cancer
Authors: Tovkai O. A. , Palamarchuk V. O. , Smolyar V. A. , Kuts V. V. , Sichinava R. M. 
Published: December 2021

Aim — to evaluate the possibility of using basal calcitonin levels in the postoperative period to assess the effectiveness of surgical treatment of medullary thyroid cancer and the likelihood of its persistence (recurrence). Materials and methods. A single-site retrospective study was conducted to assess results of surgical treatment of 194 patients (74.2 % women and 25.8 % men), from them148 (76.3 %) patients had primary forms of the disease (group 1) and 46 (23.8 %) the recurrent form (group 2). Primary surgery included thyroidectomy, supplemented with thecentral and lateral dissection of the neck. Patients in group 1 were divided into two subgroups depending on the postoperative calcitoninlevels: group 1A with normal calcitonin levels (≤ 18 pg/ml)and group 1B with hypercalcitoninemia (> 18 pg/ml). The quantitative­determination of blood serum calcitonin levels was performed using automatic immunochemiluminescent analyzer «MAGLUMI» («Snibe Diagnostic», China) in 1 week and 1 year after surgery. Accumulation and primary data processing were performed in MS Excel 2013, statistical processing was performed using StatPlus programs with descriptive statistics, parametric and nonparametric methods for testing statistical hypotheses (Student’s criteria, Mann-Whitney, Fisher angular transformation), analysis of conjugation tables, ROC-analysis. The results were considered statistically significantat p < 0.05. Results. The average duration of follow-up was 67.5 months. The results of surgery were analyzed in terms of absence or presence of clinical recurrence, calcitoninlevels in the early postoperative period (5 days) were used as a predictor. After 2 years of follow-up,normocalcitoninemiawas accompanied by recurrence in almost 2 % of cases, while hyper­calcitoninemia — in 61 % to 74 %, depending on the stage and frequency of the disease. The correlationsbetween postoperative calcitonin levels and presence of recurrence (persistence) of medullary thyroid cancer has been established: AUC = 0.928 (0.867; 0.989, Juden index (J) = 0.429, threshold (cut-off point) ≥ 28.1 pg/ml, sensitivity = 0.938 (0.854; 1,000), specificity = 0.855 (0.789; 0.920), predictive value of positive result(PPV) = 0.699, predictive value of negative resultPNV = 0.991. Moreover, countersensitivity scores and incidence of negative test results in patients with relapse depending on the level of postoperative calcitonin were calculated. Conclusions. Postoperative calcitonin levels in 5 days after surgery can be used for assessment of efficacy of the surgical treatment (AUC — 0,928 (0,867; 0,989), Juden index — 0,429)). The prognosis of recurrence-free disease does not depend on the disease stage. At calcitonin levels < 18 pg/ml, clinical signs of the disease persistence (recurrence) were detected in 1.5 % of cases (PNV = 0.991). The reliability of predicting the disease recurrence depended on the stage and frequency of surgery: PRV = 0.612 in primary forms without metasta­­ses, PRV = 0.825 in recurrent forms. Calcitonin values < 28.1 pg/ml can be considered a relatively «safe» level.