Ultrasound accurately assesses depth of invasion in T1‐T2 oral tongue cancer

BACKGROUND: Depth of invasion (DOI) is important for the T‐classification of squamous cell carcinoma of the oral tongue (SCCOT) and incorporated in the TNM 8 classification of oral cavity cancer. To determine DOI clinical palpation is performed, but the preferred radiological modality remains controversial. The aim of this study was to investigate the assessment of DOI using ultrasound (US‐DOI). METHODS: The DOI was assessed in 40 patients with T1–T3 SCCOT by ultrasound, palpation, computed tomography and magnetic resonance imaging (MRI). Histopathological DOI (H‐DOI) was gold standard. Bland–Altman analysis was used to compare mean difference and 95% limits of agreement (LOA). RESULTS: The mean difference of US‐DOI was −0.5 mm (95% LOA −4.9–4.0) compared to H‐DOI and the mean difference for MRI was 3.9 mm (95% LOA −2.3–10.2). In the subgroup analysis of cT1‐T2 the US‐DOI mean difference was 0.1 mm and the 95% LOA limits −2.5–2.7. CONCLUSIONS: Ultrasound seems to be the most accurate method to assess DOI in T1‐T2 SCCOT. MRI overestimates DOI and cannot assess a substantial proportion of the tumors. LEVEL OF EVIDENCE: 2c.