Role of solid tumor size compared with whole tumor size to predict pathologic malignant grade or prognosis in clinical stage IA lung adenocarcinoma: A multicenter study.

Abstract

7058 Background: Small lung adenocarcinoma often contains non-solid component (ground glass opacity: GGO), which is known to be low grade malignancy, on high-resolution computed tomography (HRCT). This study evaluates the usefulness of solid tumor size compared with whole tumor size on preoperative HRCT to predict pathological high-grade malignancy (positive for lymphatic invasion or vascular invasion or pleural invasion) or prognosis for clinical stage IA lung adenocarcinoma in the setting of multicenter study. Methods: We performed HRCT and fluorodeoxyglucose-positron emission tomography/CT (FDG-PET/CT) on 502 patients with clinical stage IA lung adenocarcinoma before they underwent curative surgical resection. Preoperative whole tumor size or solid tumor size on HRCT and surgical results were analyzed. Results: The median values of whole tumor size and solid tumor size were 2.0 cm and 1.2 cm, respectively. Receiver operating characteristics (ROC) area under the curve (AUC) values to predict pathological high-grade malignancy for whole tumor size and solid tumor size were 0.590 and 0.829 respectively. Multiple logistic regression analyses demonstrated that solid tumor size (p < 0.001) and maximum standardized uptake value (SUVmax) on FDG-PET/CT (p < 0.001) were independent variables relative to the prediction of pathological high-grade malignancy. Although three-year disease-free survival (DFS) rates were 92.5% for whole tumor size < 2.0 cm and 86.7% for whole tumor size > 2.0 cm (p = 0.51), three-year DFS rates were 92.0% for solid tumor size < 2.0 cm and 78.9% for solid tumor size > 2.0 cm (p = 0.048), and particularly, 100% for solid tumor size = 0 cm (pure GGO). Based on the multivariate Cox analyses, solid tumor size (p < 0.001) was a significantly independent factor for DFS as well as SUVmax (p = 0.05), but whole tumor size was not. Conclusions: Solid tumor size on HRCT has higher predictive values of pathological high-grade malignancy and prognosis than whole tumor size in clinical stage IA lung adenocarcinoma. Solid tumor size on HRCT should be considered to select therapeutic strategies for treating clinical stage IA lung adenocarcinoma.