Upfront surgery in patients with clinical skip N2 lung cancer based on results of modern radiological examinations

Background: Direct lymphatic drainage from a primary tumor to the right paratracheal or aortic window lymph nodes is often noted in pN2 disease. This multi-institutional retrospective study investigated the outcomes of upfront surgery in patients with clinical skip N2 disease (N2 disease without N1 disease) and a tumor in the right upper lobe or left upper segment based on results of modern radiological examinations, including positron emission tomography (PET). Methods: We identified 143 patients with cN2 disease who underwent upfront surgery in 12 institutions under the Thoracic Surgery Study Group of Osaka University between January 2006 and December 2013. Among 143 patients, 94 who underwent PET were analyzed. We classified these patients into Group A (n=39; clinical skip N2 disease and a tumor in the right upper lobe or left upper segment) and Group B (n=55; other). Results: The median follow-up was 56.5 months. Among the 94 patients, 50 (53.2%) had skip N2 disease and 65 (69.1%) had a tumor in the right upper lobe or left upper segment. The 5-year overall survival (OS) rates of the 94 patients with cN2 disease was 47.9%. The 5-year OS rates for the cN2pN0/1 (n=22) and cN2pN2 (n=70) groups were 74.9% and 41.2%, respectively (P=0.034). The univariate analysis of OS revealed no significant differences in age, sex, histology, carcinoembryonic antigen (CEA) level, tumor size, PET findings, and number of metastatic lymph nodes when these parameters were dichotomized. A significantly better 5-year OS rate was observed in Group A than in Group B (64.0% vs. 37.0%; P=0.039). The multivariate analysis of OS revealed that Group A was a significantly prognostic factor (P=0.030). Conclusions: Patients with cN2 disease in Group A had a more favorable prognosis. Upfront surgery may be a treatment option for such selected patients with non-small lung cancer in the specific group.