Can Unilateral Therapeutic Central Lymph Node Dissection Be Performed in Papillary Thyroid Cancer with Lateral Neck Metastasis?

Objectives: Unilateral or bilateral prophylactic central neck dissection (CND) in papillary thyroid cancer (PTC) is still controversial. We aimed to evaluate the risk factors for contralateral paratracheal lymph node metastasis and whether CND might be performed unilaterally.
Methods: Prospectively collected data of patients who underwent bilateral CND and lateral neck dissection (LND) with thyroidectomy due to PTC with lateral metastases, between January 2012 and November 2019, were evaluated retrospectively. The patients were divided into two groups according to the presence (Group 1) and absence (Group 2) of metastasis in the contralateral paratracheal region.
A total of 42 patients (46 +/- 15.7 years) were operated. In the contralateral paratracheal region, Group 1 (35.7%) had metastases, while Group 2 (64.3%) had no metastases. In groups 1 and 2, metastasis rates were 100% vs 77.8% (p=0.073), 46.7% vs 18.5% (p=0.078), and 80% vs 40.7% (p=0.023) for the ipsilateral paratracheal, prelaryngeal and pretracheal lymph nodes, respectively. The number of metastatic lymph nodes in the central region was significantly higher in Group 1 compared to Group 2 as; 10.7 +/- 8.4 vs. 2.6 +/- 2.4 (p=0.001) in bilateral central region material; 8.3 +/- 7.4 vs. 2.9 +/- 2.7 (p=0.001) in lateral metastasis with ipsilateral unilateral central region; 3.8 +/- 3.4 vs. 1.9 +/- 1.9 (p=0.023) in ipsilateral paratracheal area; and 3.7 +/- 4.6 vs. 0.6 +/- 0.9 (p=0.001) in pretracheal region, respectively. However, no significant difference was found regarding the prelaryngeal region material (0.9 +/- 1.8 vs. 0.2 +/- 0.4 (p=0.71)). Results: >2 metastatic central lymph nodes in unilateral CND material (AUC: 0.814, p<0.001, J=0.563) can estimate contralateral paratracheal metastasis with 93% sensitivity, 63% specificity, while >2 pretracheal metastatic lymph nodes (AUC: 0.795, p<0.001, J: 0.563) can estimate contralateral paratracheal metastasis with 60% sensitivity and 96.3% specificity.
Conclusion: In patients with lateral metastases, the rate of ipsilateral paratracheal metastasis is 85%, while the rate of contralateral paratracheal metastasis is 35.7%. The number of ipsilateral central region or pretracheal lymph node metastases may be helpful in predicting contralateral paratracheal lymph node metastases. Notably, unilateral CND may be performed in the presence of <= 2 metastases in the ipsilateral central region.