Importance of Ground Glass Opacity Component in Clinical Stage IA Radiologic Invasive Lung Cancer

Background. We evaluated the clinical significance of the presence of a ground glass opacity (GGO) component in clinical stage IA radiologic invasive non-small cell lung cancer (NSCLC). Methods. We reviewed 497 surgically resected clinical stage IA radiologic invasive NSCLCs, which were then classified into two groups based on consolidation tumor ratio (CTR), that is part-solid (0.5 <= CTR < 1.0, n = 177) and pure-solid (CTR = 1.0, n = 320). The part-solid tumors were subdivided into GGO-predominant (0.5 <= CTR < 0.75, n = 115) and solid-predominant (0.75 <= CTR < 1.0, n = 62) groups. Impact of tumor size was assessed based on CTR using Cox proportional hazards model. Results. Among the radiologic invasive NSCLCs, multivariate analyses revealed that the presence of the carcinoembryonic antigen and a radiologic pure-solid appearance were independent significant prognostic variables (p = 0.019 and 0.034). The 5-year overall survival (OS) revealed significant differences between pure-solid and part-solid tumors (82.7% versus 95.3%, p < 0.0001) and differed significantly among radiologic pure-solid NSCLCs in terms of maximum tumor size (<= 20 mm: 86.1%, 21 to 30 mm: 78.1%, p = 0.0274). However, oncologic characteristics between GGO-predominant and solid-predominant types are clinicopathologically similar. The 5-year OS was equivalent in the GGO-predominant and solid-predominant arms (5-year OS: 95.3% versus 96.8%, p = 0.703). Furthermore, it was identical despite the maximum tumor size (<= 20 mm: 96.6%, 21 to 30 mm: 94.9%, p = 0.4810) or the solid component size (<= 20 mm: 96.0%, 21 to 30 mm: 93.8%, p = 0.6119). Conclusions. Presence of a GGO component might have a notable impact on a favorable prognosis even in clinical stage IA radiologic invasive NSCLCs. Therefore, a clear distinction between part-solid and pure-solid findings on thin-section computed tomography is extremely important when evaluating the oncologic outcomes of radiologically solid NSCLCs. (C) 2017 by The Society of Thoracic Surgeons