Determining size in an era when size matters: Interobserver comparison of CT lung tumor size measurements and...

Limited data is available on the diagnostic performance of CT tumor size measurements in the setting of updated lung cancer management including sublobar resection for select tumors ≤2 cm, and neoadjuvant chemoimmunotherapy for tumors ≥4 cm. Our aim was to compare radiographic with pathologic tumor size and evaluate inter-radiologist variability in CT tumor size assessment.

This retrospective study included patients who underwent lung cancer resection from 1/2022-12/2023. Maximal tumor diameter on the preoperative CT report and pathology report were recorded. Diagnostic performance of CT for clinically relevant thresholds above 2 or 4 cm was examined using receiver operating characteristic (ROC) analysis. To evaluate interobserver variability, two radiologists independently measured maximal tumor diameter on CT for a subset of 92 cases and measurements were compared with intraclass correlation coefficient (ICC) and Bland-Altman analysis.

A total of 316 patients were included [median age: 69 years (IQR 64-74); 60.4% female]. Median diameter on CT was 18 mm vs 20 mm on pathology (p < 0.001). For the 2 cm threshold, CT demonstrated an AUC of 0.84, 89% sensitivity, 79% specificity. For the 4 cm threshold, CT measurement demonstrated an AUC of 0.79, 61% sensitivity, 98% specificity. Interobserver agreement between radiologists was high (ICC = 0.91, 95% CI 0.87-0.94).

While CT measurements underestimated tumor size compared to pathology, CT demonstrated strong diagnostic performance for correct pathologic size categorization for a 2 cm threshold, suggesting utility for determining lobar versus sublobar resection. For larger tumors with a threshold of 4 cm, CT demonstrated lower sensitivity, potentially leading to underutilization of neoadjuvant therapy.