Abstract
1184
Objectives: n 2017, the 8th edition of the American Joint Committee on Cancer (AJCC) cancer staging manual was released. The 8th edition includes significant modifications from the 7th edition in the sections on oral cavity cancer (OCC) and oropharyngeal cancer (OPC) that reflect differences in stage-related prognosis as a resource to guide treatment. These highlights comprise the incorporation of the depth of invasion (DOI) and exclusion of extrinsic tongue muscle involvement in the definition of the primary tumor (T) of OCC, the separation of OPC classifications based on the high-risk human papilloma virus (HPV) status, and the addition of an extranodal extension (ENE) to the definition of regional lymph nodes (N). The definition of distant metastasis (M) is the same as that in the 7th edition. Although one of the significant modifications in the 8th edition is the different clinical and pathological N classifications resulting in clinical TNM (cTNM) distinct from pathological TNM (pTNM), pathological N staging is beyond the scope of this essay. The recent introduction of integrated positron emission tomography and magnetic resonance imaging (PET/MRI) with 2-[18F]-fluoro-2-deoxy-D-glucose (18F-FDG) has demonstrated the advantages of simultaneous PET and MR imaging with higher soft-tissue contrast, multiplanar image acquisition, and functional imaging capability. 18F-FDG PET/MRI is considered to be superior to conventional imaging methods in diagnostic accuracy for local tumor invasion and the detection of lymph node metastases. Hence, we herein show the usefulness of 18F-FDG PET/MR imaging in the management of OCC and OPC patients based on the 8th edition of the AJCC cancer staging system.