Comparison of Multiplanar Reformatted CT Lung Tumor Measurements to Axial Tumor Measurement Alone: Impact on Maximal Tumor Dimension and T Stage

Abstract

The purpose of this study was to compare measurements of lung tumor size between axial and multiplanar reformatted CT images, as well as to establish whether the difference between these measurements leads to a change in T stage. Patients with lung tumors who underwent chest CT up to 31 days before lung resection between December 2010 and March 2012 were included. Axial, sagittal, and coronal CT images were evaluated by two independent readers (1 and 2) who were blinded to clinical data. In 89 patients, lung tumors categorized as T1a (54%), T1b (19%), T2a (24%), or T2b (3%) were analyzed. The longest tumor diameter using multiplanar reformatted CT was compared and correlated with axial CT alone and pathologic T stage. Statistical analysis included a Wilcoxon rank sum test to evaluate differences between measurements, intraclass correlation coefficient (ICC), and kappa statistic to assess agreement. Prediction of T stage using axial CT alone compared with multiplanar reformatted CT agreed in 82% of patients for reader 1 (κ = 0.660 [95% CI, 0.531-0.789]) and 80% of patients for reader 2 (κ = 0.695 [95% CI, 0.572-0.818]). Prediction of T stage using multiplanar reformatted CT resulted in upstaging in 18% and 20% of patients (for readers 1 and 2, respectively). Interobserver agreement (ICC [95% CI]) was 0.900 (0.803-0.954) for axial, 0.874 (0.772-0.946) for sagittal, and 0.754 (0.556-0.921) for coronal planes. Radiologic measurement of lung tumor T stage was higher using multiplanar reformatted CT as compared with axial CT alone. When available, multiplanar reformatted CT should be used to measure tumor dimension and thus assign an accurate lung cancer T stage.