Heterogeneity of Clinical N1 Non-Small Cell Lung Cancer

IntroductionThere have been many reports of N1 node metastasis on computed tomography (CT) scan, but not on positron emission tomography (PET)-CT in nonsmall cell lung cancer. The aim of this study was to analyze the clinicopathologic correlation and survival of N1 disease on preoperative PET-CT. MethodsFrom January 2003 to December 2007, 1,748 curative lung resections were performed at a single institute. We enrolled 91 patients with clinical N1 on PET-CT. All the enrolled patients had undergone pulmonary resection with mediastinal lymph node dissection. According to the preoperative PET-CT, we classified the patients into two groups: those with single N1 metastasis (cN1a, n=91) and those with multiple N1 metastases (cN1b, n=8). Clinicopathologic N staging was compared and survival analysis was performed. ResultsPathologic N2 was found in 19 (19%) patients and was more common in cN1b (4 of 8) than in cN1a group (15 of 91) (p=0.042). Overall or disease-free survival rate was not different between cN1a and cN1b in the pathologic non-N2 (p=0.723, 0.905) or in pathologic N2 (p=0.954, 0.607) subgroups. ConclusionClinical N1 on PET-CT is heterogeneous in its pathologic staging and multiple clinical N1 is more related to pathologic N2 than single clinical N1. More cases are needed to show the prognostic significance of multiple clinical N1-pathologic N2.