Accuracy of Mri in Prediction of Tumour Thickness and Nodal Stage in Oral Tongue and Gingivobuccal Cancer With Clinical Correlation and Staging

Abstract

Introduction: Squamous cell carcinoma of lower gingivobuccal complex and tongue are the most common cancer in the Indian sub-continent. The value of imaging in the staging of Oral Squamous Cell Carcinoma (OSCC) is in judging operability, assessment of the prognostic characteristics and dimensions of the primary tumour, depth of tumour invasion, the presence of cervical metastasis and detection of bone infiltration. Aim: This study evaluated squamous cell carcinomas of the oral cavity (tongue and gingivo-buccal complex) on the basis of their appearance, soft tissue extent, depth of tumour invasion and staging. Further, this study assessed the accuracy of MRI in the detection of cervical lymph nodal metastasis on the basis of ADC values on diffusion weighted MR sequence. Materials and Methods: T1- and T2-weighted MR, diffusionweighted sequences and post contrast T1W sequences were performed in various planes on biopsy proven squamous cell carcinomas (61 cases) involving tongue and/or gingivo-buccal region. Depth of tumour invasion was calculated on axial images of post contrast T1W images. The Apparent Diffusion Coefficient (ADC) was measured by using two b factors (500 and 1000 s/mm2 ). MRI findings were compared clinically and histopathologically. Results: Average depth of invasion calculated on MRI was 8.47mm and by histopathology was 6.85mm. Pearson's correlation coefficient was 0.988. Shrinkage factor was 0.8. A 71% of patients with depth of invasion greater than 9mm showed evidence of cervical lymph nodal metastasis at one or another levels. Cut-off value to discriminate between malignant and benign lymph nodes was 1.038 x10-3 mm2 /s in the present study. Conclusion: Depth of tumour invasion in oral malignancies can be measured reliably on MRI which helps in predicting cervical lymph node metastasis. Benign or malignant cervical lymph nodes can be differentiated on diffusion-weighted imaging of MRI on the basis of their ADC values.

Keywords

• apparent diffusion coefficient
• diffusion weighted imaging
• oral squamous cell carcinoma