MA10.06 Centrality Definition in Non-Small Cell Lung Cancer. Predictor For Occult Mediastinal Lymph Node Involvment

Abstract

Central tumor location is considered as an independent risk factor for occult mediastinal metastases in patients with non-small cell lung cancer (NSCLC) after negative computerized tomography (CT) and integrated positron emission tomography/CT. However, the distinction between a central and a peripheral tumor has not been codified, some authors consider any tumor in the innerthird of the hemithorax to be central, and others in the inner twothirds. The objective of this study is to identify the best centrality tumor definition for detecting occult mediastinal metastasis. We retrospectively reviewed our thoracic surgery database for cases between January 2011 and December 2015. It was identified patients with potentially operable NSCLC screened by CT and PET/CT and they were classified according to tumor location in the inner third, middle third or outer third. The prevalence of occult mediastinal lymph node metastases was analyzed in relation to tumor location. Statistical analysis for best centrality definition was performed. Univariable analysis was performed using the Fisher exact test and multivariable analysis using logistic regression. A total of 359 patients with clinical operable NSCLC were included in our study. Seventy-five (20.9%) tumors were located in the inner third, 137 (38.2%) in the middle third and 147 (40.9%) in the outer third. It was detected 23 patients with N2 disease and negative TC and PET/CT, 8/38 (21.1%) in the inner third, 6/121 (5.0%) in the middle third and 9/122 (7.4%) in the outer third. Defining centrality as tumor located in the inner third of the hemithorax the incidence of occult N2 was 21.1% and 6.2% for central and peripheral tumor respectively. And defining centrality as tumor located in the inner two-thirds the incidence of occult N2 was 8.8% for central tumors and 7.4% for peripheral. Univariable analysis shows statistical differences in occult N2 involvement between central or peripheral defining central lesion as inner third (p=0.002), but not for central definition of internal two-thirds (p=0.651). In multivariable analysis considering centrality possible definition, histology, Clinical T factor and Clinical N1 affection, only inner third as centrality definition was statistical significance predictor factor for occult mediastinal lymph node involvement (p= 0.027). Considering the results of our study the best definition for central tumor location is limited to the inner third of the hemithorax. Given the low rate of occult N2 disease in the middle third location, the systematic evaluation of the mediastinum by ecobronchoscopy and/or mediastinoscopy in this group of patients is not justified.