Role of 18-Fludeoxyglucose positron emission tomography-computed tomography and subsequent panendoscopy in head and neck squamous cell carcinoma of unknown primary.

<bold>Objectives/hypothesis: </bold>Head and neck squamous cell carcinomas of unknown primary (HNSCCUP) accounts for up to 10% of presenting head and neck squamous cell carcinomas. Identification of the primary site allows for directed therapy. Where initial investigations have failed to locate the primary site, 18-fludeoxyglucose positron emission tomography-computed tomography (PET/CT) has emerged as a useful tool with improved sensitivity over positron emission tomography alone. Following PET/CT scan, the role of subsequent panendoscopy ± biopsy has not been fully assessed. We aim to evaluate and quantify the role of PET/CT and subsequent panendoscopy in HNSCCUP.<bold>Study Design: </bold>Retrospective cohort study.<bold>Methods: </bold>Patients with HNSCCUP presenting between January 2005 and December 2010 at a regional oncology referral center were studied. All patients who presented with a metastatic neck node and unknown primary who had undergone PET/CT prior to panendoscopy were included. The accuracy of PET/CT was calculated and compared with panendoscopy and histopathological findings.<bold>Results: </bold>Fifty-two patients were included. Twenty-seven PET/CT scans suggested a primary site. Calculated diagnostic parameters were 83% sensitivity, 87% specificity, positive predictive value 89%, and negative predictive value 80%. Three false-positive PET/CT scans were noted after panendoscopy and normal histology. Importantly, three confirmed tongue base tumors were found on panendoscopy, which were undetected on PET/CT.<bold>Conclusions: </bold>PET/CT is a valuable resource for locating tumors in HNSCCUP. It helps direct biopsy and aids in the detection of local and distant metastases along with synchronous primary tumors. Importantly, due to both false-positive and false-negative PET/CT rates, panendoscopy and biopsy remains an essential adjunct investigation irrespective of PET/CT results.<bold>Level Of Evidence: </bold>4 Laryngoscope, 126:1354-1358, 2016. [ABSTRACT FROM AUTHOR]