Can We Predict the Lateral Compartment Lymph Node Involvement in RET-Negative Patients with Medullary Thyroid Carcinoma?

Abstract

Lateral lymph node dissection (LND) in the absence of macroscopic nodal metastasis remains controversial in sporadic medullary thyroid carcinoma (MTC). The aims of our study were to determine the risk of lateral lymph node (LN) metastases with a focus on lateral contralateral N1, and to define a risk-adapted surgical treatment for these patients. All patients who underwent surgery from 1980 to 2012 for previously untreated RET-negative MTC were reviewed. We focused on the lateral compartments of LN metastases and identified three groups: no lateral LN metastases, ipsilateral lateral (ILL)-LN metastases with no contralateral LN involvement, and contralateral lateral (CLL)-LN metastases. Overall, 131 patients underwent surgery for RET-negative MTC. A total thyroidectomy with LND was performed in 112 patients (85%), including 97 patients who had an ILL-LND and 92 patients who had a CLL-LND. Lateral LN metastases (N1) occurred in 40 patients (37%): 31 patients (32%) had ILL-LN metastases with no contralateral LN involvement, and 9 patients (10%) had CLL-LN metastases. The preoperative cut-offs for LN metastases in the ILL compartment were very low, with a smallest tumor size of 5mm, and lowest serum calcitonin level of 38pg/ml. Disease-free survival rates decreased from 92% for patients with no lateral LN metastases to 41% for patients with ILL-LN metastases and 0% for patients with CLL-LN metastases. ILL-LND should be performed in every patient and only a minority of MTC patients with small micro-MTC, and low serum calcitonin levels should not have a CLL-LND.