Subtraction CT Improves Detectability of Mandibular Bone Invasion in Oral Squamous Cell Carcinoma

Pretreatment evaluation of bone invasion in head and neck cancer is critical for treatment strategies. We investigated the usefulness of subtraction CT (SCT) in evaluating mandibular bone invasion in oral squamous cell carcinoma (OSCC). This retrospective investigation included patients with OSCC who underwent surgery at the Shizuoka Cancer Center Hospital between 2018 and 2022. We evaluated tumor invasion of the mandibular bone by interpreting conventional computed tomography (CT), SCT, and magnetic resonance imaging (MRI) and comparing the findings with the pathological examination. Sensitivity and specificity were compared using the McNemar test, whereas Spearman's correlation and Bland-Altman methods were utilized to assess mandibular bone invasion depth. A total of 71 patients were enrolled. SCT showed significantly higher sensitivity than conventional CT for evaluating mandibular marrow invasion (97.2% vs. 80.6%, p = 0.031). In the evaluation of mandibular canal involvement, SCT showed significantly higher specificity than MRI (95.9% vs. 81.6%, p = 0.016). Furthermore, SCT demonstrated the highest correlation with pathological bone invasion depth (correlation coefficients: CT = 0.933, SCT = 0.950, MRI = 0.908; all p