Risk Factors for Central Compartment Lymph Node Metastasis in Papillary Thyroid Microcarcinoma: A Meta-Analysis.

Background: The surgical management of papillary thyroid microcarcinoma (PTMC), especially regarding the necessity of central lymph node dissection (CLND), remains controversial. This meta-analysis was conducted to investigate the clinicopathologic factors predictive of central compartment lymph node metastasis (CLNM) in patients diagnosed with PTMC.

Methods: PubMed, EMBASE, Ovid, Web of Science, and the Cochrane Library were searched from their inception to September 2013. Published studies that explored the association between clinicopathologic factors and CLNM in PTMC patients were included. From the identified studies, we extracted the number of individuals with or without each risk factor to calculate the CLNM-positive proportions and used fixed/random-effects models for the meta-analyses of overall relative risk (RR). The pooling analysis on the association between CLNM or the different CLNDs and prognosis was also conducted.

Results: A total of 19 eligible studies that included 8345 patients were identified. Three studies did therapeutic CLND, while the other 16 studies performed prophylactic CLND in PTMC patients. Meta-analyses revealed that CLNM was associated with male gender (RR = 1.36; 95 % CI 1.22-1.52, p = 0.001), younger age (<45 years; RR = 1.15; 95 % CI 1.04-1.27, p = 0.006), larger tumor size (>5 mm; RR = 1.51 95 % CI 1.32-1.65, p = 0.001), multifocality (RR = 1.40; 95 % CI 1.27-1.54, p = 0.001), and extrathyroidal extension (RR = 1.81; 95 % CI 1.34-2.43, p = 0.001). Meta-regression analysis indicated that a disparity in the proportion of PTMC patients with CLNM in each study was the main factor resulting in heterogeneity among the 19 studies. In addition, the pooling analyses suggested that CLNM did not significantly predict neck recurrences [hazard ratio (HR) = 0.95, 95 % CI 0.67-1.22, p = 0.054], and the prophylactic CLND group did not improve local control significantly compared to the therapeutic group (RR = 0.96, 95 % CI 0.46-2.01, p = 0.544).

Conclusion: Prophylactic CLND may be performed in PTMC patients with clinically uninvolved central lymph nodes but with high risk factors; multicenter studies with long-term follow-up are recommended to better understand the risk factors and surgical management for central nodes in PTMC.