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.