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PET/CT Useful for Head and Neck Cancers, with Limitations

by Amy Eckner •

How does combined positron emission tomography and computed tomography (PET/CT) compare with CT and magnetic resonance imaging (MRI) for monitoring head and neck cancer?

Background: PET/CT is the most sensitive of the currently available standardized imaging modes and is widely used for tumor staging and assistance in identifying cancer metastatic to the cervical lymph nodes from a primary that has not been identified; however, false positives can be common. To date, no good data exist regarding the costs related to false positives on PET/CT.

Study design: Study of selected literature from contemporary publications on the use of PET/CT, interpreted by expert opinion.

Setting: Departments of Otolaryngology and Radiology, University of Pittsburgh School of Medicine.

Synopsis: Approximately 2% to 9% of all patients with head and neck cancer present with metastatic cancer in the cervical lymphatics from an unknown primary (CUP) that is difficult or impossible to find with physical examination, panendoscopy, conventional imaging, and blind biopsies. In the literature, PET/CT helped identify CUP in approximately one-third of all cases. PET/CT provided recurrent disease recognition on average six to 12 months before clinical recognition; however, it was unknown whether PET/CT resulted in improved disease-free survival. Whole body PET/CT identified many thyroid lesions that were incidental to the primary tumor. The authors made recommendations that PET/CT should not be used sooner than eight weeks after completion of therapy for surveillance due to false positives; that PET/CT should not be used in diagnostic evaluation until a malignant diagnosis has been made; that it is not indicated for Stage I/II tumors; and that it should not be used for glandular tumors that are notoriously non-avid for fluorodeoxyglucose. Study limitations included the inability to determine the interval at which PET/CT should be repeated in negative post-treatment surveillance and the inability to distinguish among squamous cancers that occur at different sites or between HPV1 and HPV2 squamous cell carcinoma.

Bottom line: PET/CT is useful for patients with advanced-stage squamous cancer of the head and neck, but there are limitations to its use and more evaluation is needed to compare it to CT or MRI for post-treatment monitoring.

Citation: Johnson JT, Branstetter BF IV. PET/CT in head and neck oncology: state-of-the-art 2013; Laryngoscope. 2014;124:913-915.