Computed tomography-derived depth of invasion in lip squamous cell carcinoma: radiologic-pathologic correlation and...

To evaluate the association, agreement, and reproducibility of contrast-enhanced computed tomography (CT)-derived depth of invasion (rDOI) compared with pathological depth of invasion (pDOI) in lip squamous cell carcinoma.

This retrospective single-center study included 51 patients who underwent preoperative contrast-enhanced CT between January 2010 and April 2024. Two observers independently measured rDOI, tumor thickness, and maximum tumor diameter twice. Pathological measurements served as the reference standard. Correlation, Bland-Altman agreement, mean absolute error, classification performance at pDOI thresholds of >5 mm and >10 mm, and intraobserver and interobserver reproducibility were assessed.

Mean pDOI was 6.48 ± 4.67 mm; mean rDOI was 5.87 ± 4.11 mm for observer 1 and 6.77 ± 4.64 mm for observer 2. rDOI correlated significantly with pDOI (r = 0.685 and 0.781; both p < 0.001). Mean CT-pathology biases were -0.61 and 0.29 mm, but the 95% limits of agreement were wide. Mean absolute errors were 3.08 and 2.75 mm. Classification accuracy was 72.9% at the >5-mm threshold and 83.3% at the >10-mm threshold for both observers, although sensitivity varied at >10 mm. Interobserver reproducibility was excellent for DOI, tumor thickness, and maximum tumor diameter.

CT-derived DOI was reproducible in measurable lip squamous cell carcinomas but was not interchangeable with pDOI. It should be used as an adjunctive preoperative estimate rather than as a stand-alone basis for DOI-based staging or surgical management.