Prognostic impact of a ground glass opacity component in the clinical T classification of non-small cell lung cancer

Objective: To determine whether solid component size and the presence of a ground glass opacity (GGO) component are independently associated with survival outcomes in patients with early-stage non-small cell lung cancer (NSCLC) using the eighth edition Lung Cancer Stage Classification. Methods: We retrospectively evaluated 1029 surgically resected early-stage NSCLCs. T categories were assigned based on solid component size using the eighth classification. All tumors were classified into 1 of 2 groups: the GGO group or the solid group. We evaluated the prognostic impact of several clinicopathological variables in clinical T classification using a Cox proportional hazard model. Results: On multivariable analysis, the presence of a GGO component (hazard ratio [HR], 0.314; 95% confidence interval [CI], 0.181-0.529: P < .001) and solid component size (HR, 1.021; 95% CI, 1.006-1.036; P = .006) were identified as independently significant prognostic factors of overall survival. However, after accounting for the presence of a GGO component, neither maximum tumor size nor solid component size added to the prediction of long-term survival. Moreover, tumor size significantly affected survival outcome only in the solid group (HR, 1.020; 95% CI, 1.006-1.034; P = .004). Survival was excellent at >= 90% despite the revised T categories, provided that the tumor had a ground glass appearance. Meanwhile, tumor size significantly affected survival only in the solid group (P < .001). Conclusions: The presence of a GGO component is a significant prognostic factor in early-stage NSCLC. External validation is required to assess whether it should be adopted as a novel factor in clinical T staging.