Impact of Invasive Extranodal Extension on the Prognosis of Patients with Papillary Thyroid Carcinoma

Background: Although 20-50% of papillary thyroid carcinoma (PTC) patients initially present with lymph node metastases, prognosis is excellent. Thus, the significance of lymph node metastasis in PTC remains controversial. In this study, we examined the impact of extranodal extension to surrounding organs (invasive extranodal extension) on the prognosis for PTC patients. Methods: Medical records of PTC patients who underwent surgery as their initial treatment at our institution between 1981 and 2008 were retrospectively reviewed. Patients with or without invasive extranodal extension were selected. Our therapeutic strategy for PTC with invasive extranodal extension included complete resection and functional reconstruction. Intergroup comparison was performed using Student's t-test or the chi-square test as appropriate. Survival curves determined by the Kaplan-Meier method were compared for statistical significance using the log-rank test. A Cox-hazard regression model with the forward stepwise method was used for multivariate analysis. Results: The study cohort included 60 (12.3%) patients with and 428 (87.7%) without invasive extranodal extension. The most common site of invasive extranodal extension in the central neck compartment was the recurrent laryngeal nerve, whereas the internal jugular vein was the most frequently invaded site in the lateral neck compartment. The locoregional recurrence rate did not differ significantly between patients with and without invasive extranodal extension, but the distant recurrence rate was higher for those with invasive extranodal extension. The 10-year disease-specific survival rate was significantly lower for patients with invasive extranodal extension than for those without invasive extranodal extension. Furthermore, multivariate analysis revealed that being aged >= 45 years, poor differentiation, and extrathyroidal extension were independent predictive factors for disease-specific death in PTC. Invasive extranodal extension had no effect on the survival of PTC patients. Conclusions: Invasive extranodal extension did not affect the survival of patients with PTC. Despite a negative impact on distant recurrence, invasive extranodal extension did not affect locoregional recurrence in PTC patients.