Risk factors for contralateral central lymph node metastasis in unilateral cN0 papillary thyroid carcinoma: A meta-analysis

Central lymph node metastasis(CLNM) is common in papillary thyroid carcinoma(PTC). LNM is related to local recurrence and adverse prognosis. The extent of prophylactic central lymph node dissection(pCLND) is not well defined. We aim to investigate the prevalence and risk factors for contralateral central lymph node metastasis (CCLNM) in unilateral clinical node-negative (cN0) PTC patients to determine the appropriate extent of pCLND.A systematic literature search was performed using PubMed and Embase databases until May 2018. Published studies that estimated the association between clinicopathologic factors and CCLNM were included.A total of 6 studies involving 1399 patients were included. The prevalence of CCLNM was 10.9% in all patients. The pooled analysis revealed that male gender (pooled OR = 1.67, 95%CI = 1.11-2.53, p = 0.015), age<45years (pooled OR = 1.97, 95%CI = 1.37-2.85, p < 0.001), lymphovasular invasion (pooled OR = 4.23, 95%CI = 2.25-7.98, p < 0.001), extrathyroid invasion (pooled OR = 1.75, 95%CI = 1.08-2.83, p = 0.023), and ipsilateral CLNM (pooled OR = 12.26, 95%CI = 7.27-20.67, p < 0.001) were significant risk factors for CCLNM. While tumor size>1 cm (pooled OR = 3.39, 95%CI = 0.83-13.88, P = 0.090), capsular invasion (pooled OR = 1.28, 95%CI = 0.79-2.06, p = 0.313), extrathyroid extension (pooled OR = 1.49, 95%CI = 0.86-2.56, p = 0.152), and MACIS≥6 (pooled OR = 1.08, 95%CI = 0.51-2.26, p = 0.844) were not significantly associated with CCLNM.Our meta-analysis identified that male gender, age<45years, lymphovasular invasion, extrathyroid invasion and ipsilateral CLNM were significant risk factors for CCLNM. These findings may guide the extent of pCLND in unilateral cN0 PTC patients.