(522) Ultrasound Accurately Assesses Depth of Invasion in Oral Tongue Cancer

Introduction: 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) between 2019 and 2021. Histopathological DOI (H-DOI) was gold standard. Bland-Altman analysis was used to compare mean difference and 95% limits of agreement (LOA).

Results: Ultrasound could measure DOI in all patients. Lingual nerve block was effective anaesthesia in 100% (7 out of 7) of the patients with painful tumors. MRI could not measure DOI in 21% (8 out of 38) of the patients. The mean difference of US-DOI was -0.5mm (95% LOA -4.9 to 4.0) compared to H-DOI and the mean difference for MRI was 3.9mm (95% LOA -2.3 to 10.2). In the subgroup analysis of cT1-T2 the US-DOI mean difference was 0.1mm and the 95% LOA limits -2.5 to 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. Lingual nerve block can aid the preoperative assessment of tongue cancer, including DOI.