Clinical Implications of Bilateral Lateral Cervical Lymph Node Metastasis in Papillary Thyroid Cancer: A Risk Factor for Lung Metastasis

Abstract

Distant metastasis to the lung in papillary thyroid cancer (PTC) is rarely detected, but it is known to be an important prognostic factor associated with survival. We investigated risk factors for lung metastasis in PTC. We performed a retrospective review of patients with PTC (n=977) who were treated from January 2006 to August 2009. Enrolled patients received radioablation therapy followed by a radioiodine whole body scan. Lung metastasis was screened out with whole body scan or positron emission tomography/computed tomography (PET/CT) and confirmed with chest CT. Age, gender, extrathyroidal extension, central lymph node metastasis, lateral lymph node metastasis, and bilateral lateral cervical lymph node metastasis (BLNM) were investigated to analyze the relationship with lung metastasis. In total, 949 patients were enrolled. The median age was 49 years (±13 years) with 829 women. Lung metastasis was found in 20 patients (2.1%). Patients were divided into three groups by tumor size (≤1 cm, 1-2 cm, >2 cm); the groups comprised 47.3%, 28.5%, and 24.1% of the patients, respectively. BLNM was identified in 4.4% (n=43). In a univariate analysis, male gender, old age, large tumor, extrathyroidal extension, lymph node metastasis, lateral lymph node metastasis, and BLNM were significantly related to lung metastasis (P<0.05). In a multivariate analysis, BLNM appeared to be the only significant risk factor for lung metastasis (P=0.026; odds ratio=10.219). BLNM may be a risk factor for lung metastasis. This indicates that careful examinations, including chest CT and positron emission tomography (PET), are recommended during the follow-up period when BLNM is suspected.