Is a CT Scan Reliable for Determining the Depth of Invasion in Patients with Oral Tongue Squamous Cell Carcinoma? An Original Study and Literature Review

Abstract

Background: Depth of invasion (DOI) in oral tongue squamous cell carcinoma (OTSCC) is an important prognostic factor influencing tumor staging, surgical planning, and overall prognosis. Objectives: This study aimed to assess the correlation between computed tomography-based radiologic DOI (rDOI) and pathologic DOI (pDOI) and to evaluate the diagnostic accuracy of computed tomography-based rDOI, using pDOI as the gold standard. Patients and Methods: This retrospective, single-center diagnostic accuracy study included 60 consecutive eligible patients with biopsy-proven OTSCC who underwent preoperative contrast-enhanced computed tomography at an academic referral center between April 2022 and March 2023. Patients with recurrent tumors, prior head-and-neck radiotherapy, computed tomography artifacts precluding measurement, or missing pathological DOI were excluded. The index test, computed tomography-derived rDOI, was measured independently by two blinded radiologists with 5 and 20 years of head-and-neck imaging experience and compared with histopathological DOI as the reference standard, assessed by a dedicated head-and-neck pathologist blinded to imaging findings. The primary analysis evaluated agreement and diagnostic accuracy. Inter-reader reliability and the association between DOI and nodal involvement were prespecified secondary objectives. Results: Sixty patients were analyzed, including 35 men and 25 women, with a mean age of 54.0 ± 14.2 years. The mean pDOI was 10.71 ± 6.47 mm. Computed tomography systematically overestimated the pDOI by 1.12 mm for Radiologist 1 and by 2.19 mm for Radiologist 2. Lymph node involvement was present in 15 patients (25%), who had a significantly higher pDOI than those without lymph node involvement (14.13 vs. 8.91 mm; P = 0.002). Strong agreement was observed between pDOI and rDOI, particularly for DOI > 5 mm. For Radiologist 1, κ = 0.797 (95% confidence interval [CI]: 0.69 - 0.91), Spearman's rho = 0.668 (95% CI: 0.53 - 0.77), and P < 0.001. For Radiologist 2, κ = 0.700 (95% CI: 0.59 - 0.81) and P < 0.001. For detecting DOI > 5 mm, computed tomography showed an area under the curve of 0.934 for Radiologist 1 and 0.921 for Radiologist 2, with sensitivity > 89% and specificity > 85%. Inter-reader agreement was excellent (κ = 0.838; 95% CI: 0.76 - 0.92; Spearman's rho = 0.945; P < 0.001) and was independent of patient sex or lymph node status. Conclusion: Computed tomography-based rDOI is a reliable and diagnostically accurate preoperative tool for OTSCC staging, particularly for tumors with DOI > 5 mm. It may serve as a useful preoperative surrogate estimate of DOI when surgical pathology is not yet available. Ultrasound may be more accurate for superficial lesions with DOI ≤ 5 mm.