[The clinical value of preoperative calcitonin levels in predicting upper mediastinal lymph node metastasis in thyroid medullary carcinoma].

<b>Objective:</b> To investigate the correlation between preoperative calcitonin levels and upper mediastinal lymph node metastasis in medullary thyroid carcinoma (MTC). <b>Methods:</b> A retrospective analysis was conducted on 249 MTC patients who underwent surgery at the Cancer Hospital, Chinese Academy of Medical Sciences between January 2010 and December 2021. Based on postoperative pathology, patients were categorized into the upper mediastinal lymph node metastasis group (<i>n</i>=41) and the non-upper mediastinal lymph node metastasis group (<i>n</i>=208). Clinicopathological features were compared, and survival outcomes were assessed using Kaplan-Meier analysis. Receiver operating characteristic (ROC) curves were employed to determine the predictive efficacy and optimal cutoff value of preoperative calcitonin for the upper mediastinal lymph node metastasis group. Logistic regression identified independent risk factors for the upper mediastinal lymph node metastasis group. <b>Results:</b> Compared to the non-upper mediastinal lymph node metastasis group, the upper mediastinal lymph node metastasis group demonstrated a higher proportion of male patients, elevated levels of carcinoembryonic antigen and calcitonin, increased multifocality, larger primary tumor size, higher rates of extrathyroidal extension, advanced T and N stages, and greater incidences of lymph node metastasis and extracapsular invasion (all <i>P</i>＜0.01). Patients with upper mediastinal lymph node metastasis exhibited significantly lower overall survival than those without upper mediastinal lymph node metastasis (<i>P</i>＜0.001). ROC curve analysis revealed an area under the curve of 0.783 for preoperative calcitonin in predicting upper mediastinal lymph node metastasis, with an optimal cutoff value of 1 865 pg/ml (sensitivity 71.79%, specificity 75.53%). Multivariate logistic regression analysis identified preoperative calcitonin levels >1 865 pg/ml (<i>OR</i>=5.31, 95% <i>CI</i>: 1.77-15.94) and >15 metastatic lymph nodes (<i>OR</i>=4.90, 95% <i>CI</i>: 1.87-12.89) as independent risk factors for the upper mediastinal lymph node metastasis group. <b>Conclusions:</b> Preoperative calcitonin＞1 865 pg/ml suggests a higher likelihood of MTC with upper mediastinal lymph node metastasis. For individuals with suspected upper mediastinal lymph node metastasis on imaging, combining preoperative calcitonin levels can reduce false-positive rates.