@article {Amit1282, author = {Uri Amit and Leo Baron and Ella Nissan and Israel Sandler and Damien Urban and Iris Barshack and Zvi Symon and Tima Davidson}, title = {Does 18F-FDG-PET/CT Improve Detection and Management of Cancers with Unknown Primary Site?}, volume = {60}, number = {supplement 1}, pages = {1282--1282}, year = {2019}, publisher = {Society of Nuclear Medicine}, abstract = {1282Background: Cancer of unknown primary site (CUP) is a relatively common clinical entity, with a wide variety of presentations and histologies. Conventional radiological imaging enables detection of 25\% of the primary sites of these cancers, while the role of 18F-fluorodeoxyglucose (FDG) PET/computed tomography (CT) in this context has not been completely defined. The aim of this study was to assess the role of 18F-FDG PET/CT in the identification and management of CUP. Methods: We reviewed the records of consecutive patients with CUP, referred for 18F-FDG PET/CT during April 2012 - February 2018. Patient demographics, tumor histology and imaging studies were obtained from the hospital{\textquoteright}s clinical database. Results: The study comprised 57 patients (31 males), mean age 64.5 {\textpm} 14.5 years (range: 21-91). The mean SUV max was 10.6{\textpm}6.2 (range 2.2-27.8). The most common sites of 18F-FDG uptake were the lymph nodes: 18 (32\%), bones: 8 (14\%) and the liver: 7 (12\%). The tumors were classified into five broad categories: tumors where the origin can be presumed 31 (54\%), poorly differentiated carcinoma 10 (17.5\%), squamous cell carcinoma 9 (16\%), adenocarcinoma 5 (9\%) and neuroendocrine carcinoma 2 (3.5\%). 18F-FDG PET/CT diagnosed the primary tumor in 28 (49\%) patients. In univariate analysis, tumor pathology was the only variable examined that was associated with a diagnosis of the primary tumor by 18F-FDG PET/CT; detection rates were high in neuroendocrine carcinoma and when the tumor origin could be presumed by pathology. However, 18F-FDG PET/CT did not detect any tumors of squamous cell carcinoma histology. Of the 28 patients for whom 18F-FDG PET/CT was diagnostic, 21 (75\%) received systemic treatment specific for their tumor, two had surgery with curative intent and two had palliative radiotherapy. Conclusion: 18F-FDG PET/CT has considerable ability to detect and guide treatment management in the setting of CUP and negative conventional imaging. However, it does not appear beneficial in a subgroup of patients with squamous cell carcinoma histology.}, issn = {0161-5505}, URL = {https://jnm.snmjournals.org/content/60/supplement_1/1282}, eprint = {https://jnm.snmjournals.org/content}, journal = {Journal of Nuclear Medicine} }