Effect of Computed Tomography Window Settings and Reconstruction Plane on 8th Edition T-stage Classification in Patients with Lung Adenocarcinoma Manifesting As a Subsolid Nodule

Purpose: To assess the effect of window settings and reconstruction plane on clinical T-stage determined by solid portion size within subsolid nodules (SSNs), based on 8th-edition TNM standards.

Materials And Methods: This retrospective study included 247 SSNs from 221 patients who underwent surgery for lung adenocarcinomas between Feb 2012 and Oct 2015. Two radiologists independently measured the diameter of the solid portion on axial, coronal, and sagittal planes using lung- and mediastinal-window. The largest diameter among the measurements on the three planes was referred to as multiplanar measurement. Inter-reader agreement as well as the correlation between the CT and pathologic measurements were calculated using intra-class correlation coefficients (ICCs). The proportions of disagreement in clinical T-stage on different measurement methods were measured. The κ values for agreement between clinical- and pathological T-stage were measured.

Results: Inter-reader agreement was moderate-to-excellent (ICC confidence interval [CI] range, 0.51-0.92) in lung-window, while it was good-to-excellent (0.77-0.95) in mediastinal-window. The correlation between the CT and pathologic measurements was good-to-excellent (ICC CI range, 0.63-0.82) in lung-window and fair-to-good (0.25-0.78) in mediastinal-window. The proportions of disagreement between clinical T-stages using mediastinal- and lung-window were 32.0%-41.7% and 33.6%-49.0% with axial and multiplanar measurement, respectively. Multiplanar measurement resulted in upstaging in 12.6%-15.8% and 19.0%-24.3% of cases with mediastinal- and lung-window, respectively, when compared with axial measurement alone. The κ values for agreement between clinical T-stage and pathological T-stage ranged from 0.53 to 0.69.

Conclusions: Mediastinal-window was a more stable method in the aspect of the inter-reader agreement, but the correlation between the CT and pathologic measurement was better in lung-window. The clinical T-stage varied in up to one-half of the cases according to the window setting, and multiplanar measurement resulted in upstaging in up to one-fourth of the cases.