Which Window Setting Is Best for Estimating Pathologic Invasive Size and Invasiveness?

In the Eighth Edition of the Tumor Node Metastasis Classification System for Lung Cancer, the definitions of the clinical T and pathologic T descriptors have changed. Little has been reported on comparisons between the consolidation diameter in the lung window setting and the tumor diameter in the mediastinal window setting with respect to the correlations with pathologic invasive size (IS) and invasiveness. The present study was conducted to clarify which window setting was better for preoperatively estimating IS and invasiveness.

We retrospectively reviewed 1,167 consecutive patients with lung adenocarcinomas measuring 3 cm or less in diameter. We measured three high-resolution computed tomography variables and examined correlations of IS with these variables, factors predictive of an IS of 5 mm or less, and other variables related to invasiveness.

On receiver operating characteristic curve analysis, the tumor diameter in the mediastinal window setting more strongly predicted IS than did the consolidation diameter in the lung window setting (p < 0.001), and the consolidation diameter in the lung window setting more strongly predicted IS than did the maximum tumor diameter in the lung window setting (p < 0.001). Lymphatic, vascular, and pleural invasion were best predicted by the tumor diameter in the mediastinal window setting.

We can estimate IS and other variables related to invasiveness most precisely by measuring the tumor diameter in the mediastinal window setting. The tumor diameter in the mediastinal window setting is an important variable that we should measure preoperatively.