Oral cavity squamous cell carcinoma: role of pretreatment imaging and its influence on management.

ABSTRACT

Squamous cell carcinoma (SCC) is the commonest malignancy in the oral cavity. The oral cavity has several subsites. Knowledge of the patterns of disease spread at each subsite with the impact on treatment and prognosis provides a deeper understanding of the role of imaging. Information from imaging helps accurate staging, assess resectability, and plan multimodality treatment. Mandibular erosion, posterior soft tissue extent, and perineural spread influence treatment and prognosis in gingival, buccal, and retromolar trigone (RMT) cancers. Multidetector computed tomography (MDCT) with multiplanar reformations and bone and soft tissue algorithms provides the highest specificity for bone erosion. Hard palate SCC is optimally imaged with contrast-enhanced magnetic resonance imaging (MRI) to detect perineural spread. In oral tongue and floor of the mouth (FOM) SCC, extrinsic muscle invasion, extension across the midline, extent of posterior and inferior spread, and proximity to the hyoid are issues that impact therapeutic options. Contrast-enhanced MRI is the optimal imaging method for staging the primary due to its superior soft tissue resolution. In oral tongue SCCs with tumour thickness ≤4 mm, elective neck dissection can be avoided. For nodal staging (N-staging), all imaging methods are comparable, but fall short of surgical staging. Sentinel lymph node biopsy has a promising role in N-staging. Positron emission tomography (PET)/integrated PET/CT has no role in evaluating the clinically negative neck. PET/CT has a role in pretreatment evaluation of advanced oral cavity SCC for depicting distant metastases and for mapping nodal extent in the clinically positive neck. Diffusion-weighted MRI, dynamic contrast-enhanced MRI, and CT perfusion have a potential role as baseline pretreatment studies for response assessment to chemoradiation in advanced oral cavity SCC.