The ground glass opacity component can be eliminated from the T-factor assessment of lung adenocarcinoma

The radiological ground glass opacity (GGO) component of an adenocarcinoma pathologically reflects a non-invasive adenocarcinoma in situ (AIS). Measuring the tumour diameter to include the GGO component may overestimate the T factor. In this retrospective study, we evaluated the effect of the GGO component on the recurrence of an adenocarcinoma. We reviewed patients who underwent a surgical resection of a lung adenocarcinoma and were pathologically proven to be T1-2N0M0, from 1999 to 2009. We conducted four different types of analyses (multivariate analysis, receiver operating characteristic [ROC] analysis, survival analysis according to subcategories and survival analysis of propensity score-matched pairs) to evaluate the impacts of GGO and the solid component on recurrence. The study included 241 patients, and there were 34 recurrences. Sixty-eight cases with AIS and minimally invasive adenocarcinoma exhibited 100% recurrence-free survival. A univariate and a multivariate analysis revealed that the maximum tumour diameter measured in the mediastinal window was a better prognostic factor than the maximum tumour diameter in the lung window. This finding was supported by an ROC curve analysis, a subgroup analysis and a propensity score-matched analysis. An ROC curve analysis revealed that GGO component exclusion resulted in improved prognostic performance for recurrence and pathological vessel invasion. A subgroup analysis and a propensity score-matched analysis demonstrated that tumours with similar solid component sizes and different GGO sizes exhibited equivalent recurrence-free survival. The GGO component showed little influence on recurrence. Recurrence-free survival was solely dependent on the solid component size. A T factor measured by the solid component may be a more accurate prognostic parameter.