Prognostic impact of extra‐nodal extension in thyroid cancer: A meta‐analysis

BACKGROUND AND OBJECTIVES: Lymph node involvement is common in thyroid cancer, but the system of staging does not consider the histological features of lymph node metastases. We conducted a meta-analysis to investigate the prognostic role of extranodal extension (ENE) in thyroid cancer patients. METHODS: We ran PubMed and SCOPUS searches without language restrictions. Prospective studies reporting data on overall mortality, cancer-specific mortality, or disease recurrence including thyroid cancer patients, in which cases with ENE (ENE+) were compared with those with only intranodal disease (ENE-) were eligible. Data were summarized using risk ratios (RR) for number of deaths/recurrences, and hazard ratios (HR) for time-dependent risks related to ENE+ status, adjusted for potential confounders. RESULTS: Of 414 hits, 23 studies were eligible and included. Compared to ENE-, patients who were ENE+ had significantly higher rates of all-cause mortality (studies = 8; RR = 3.25; 95%CI: 1.35-2.64, I(2) = 83%) and recurrence (studies = 17; RR = 2.64, 95%CI: 1.93-3.60, I(2) = 73%). Using HRs adjusted for potential confounders, ENE+ status carried a significantly higher risk of all-cause and cancer-specific mortality and disease recurrence. CONCLUSION: It becomes mandatory to consider ENE in the histopathological examination of surgical samples in thyroid cancer patients, and this factor should be included in future oncological staging systems.