Role of 18FFDG PET/CT in the Treatment of Head and Neck Cancers: Posttherapy Evaluation and Pitfalls

Abstract

n the United States, extracranial head and neck carcinomas constitute 2–3% of cancers [1], whereas globally they represent 5.4% of all cancers (unpublished data from summary lecture notes, American Society of Head and Neck Radiology). Most head and neck cancers are squamous cell carcinomas of the larynx, nasopharynx, and oral cavity. Accurate initial staging of head and neck malignancies is critical in establishing the prognosis and in selecting the treatment for these patients. After treatment, the complex anatomy in this region is further complicated by postsurgical or radiation changes with the loss of the imaging landmarks and symmetry and with marked distortion of the normal anatomy, making the distinction between posttherapy changes and recurrence or residual tumor challenging. In these situations and in the detection of unknown primary tumors, distant metastases, and synchronous primary tumors, PET with 18F FDG is a better imaging technique than either CT or MRI [2–5]. PET alone, however, has lower spatial resolution than CT or MRI. Fused PET/CT, described by Beyer et al. [6], combines the anatomic detail provided by CT with 18F FDG PET metabolic information, thereby increasing accuracy in the detection of tumor [7].