Nasopharyngeal carcinoma: ¹⁸F-fluorodeoxyglucose-positron emission tomography

Nasopharyngeal carcinoma (NPC) is an epithelial malignancy that occurs worldwide with particularly high frequency in southern China, parts of Southeast Asia, Northern Africa, and Alaska. The etiological factors for endemic NPC include Epstein-Barr virus, environmental factors, and genetic susceptibility. 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) is a unique imaging modality for functional evaluation of NPC. PET is a whole-body functional imaging technique that provides information about tissue metabolism. FDG-PET helps in the evaluation of head and neck malignancy by pinpointing the regions of accelerated glucose metabolism using the radionuclide FDG. It facilitates the identification of viable tumors within the fibrotic areas in the irradiated field and helps to differentiate tumor recurrence from post-treatment inflammation. Since FDG-PET can scan the whole body, it has another advantage of disclosing distant metastasis in a single session. However, due to its inherent relatively poor anatomic resolution, FDG-PET cannot accurately define the local anatomic extent of the tumor and thus cannot be used in isolation for tumor staging. FDG-PET has a role in accurate mapping of nodal spread and in delineating tumor-bearing tissue for the planning of conformal radiotherapy. By virtue of its high sensitivity in disclosing unexpected distant metastasis, FDG-PET is most feasible in NPC patients with advanced nodal stage.