Identification of Early T1b Lung Adenocarcinoma Based on Thin-Section Computed Tomography Findings

Introduction: The aim of this study was to radiologically identify early lung adenocarcinoma in clinical T1bN0M0 lung cancer, based on pathological findings and long-term prognosis. Methods: In this study, we reviewed lung nodules findings on thin-section computed tomography in 173 patients with clinical T1bN0M0 lung adenocarcinoma who underwent surgery between 2003 and 2007. The ratio of the size of solid attenuation to the maximum tumor dimension (consolidation/tumor [C/T] ratio) was calculated. We defined two groups of patients by C/T ratio cutoff levels of 0.00, 0.25, 0.50, 0.75, and 1.00 and compared the rates of pathological nonaggressive lung adenocarcinoma, overall survival, and recurrence rates between the groups. The percentages of predominant histological subtypes were compared between two groups divided by the optimal cutoff level. Various clinical factors were analyzed by univariate and multivariate analyses to predict pathological lymph node involvement. Results: The median follow-up period was 62 months. All patients with C/T ratios of 0.5 or less were diagnosed as having pathological nonaggressive adenocarcinomas, and there was no recurrence; their 5-year overall survival rate was 97.4%, which was significantly better than that for patients with C/T ratios of greater than 0.5 (76.2%). None of the ground-glass opacity-predominant tumors were predominantly solid adenocarcinoma with mucin. The C/T ratio of 0.5 or more was an independent predictor of lymph node involvement. Conclusion: In patients with clinical T1bN0M0 disease, the C/T ratio of 0.5 or less identified early lung adenocarcinoma. In patients with the identified early disease, a feasibility study of limited surgery may be warranted.