The role of fluorodeoxyglucose positron emission tomography in cervical lymph node metastases from an unknown primary tumor

Abstract BACKGROUND The authors performed a comprehensive review of the efficacy of fluorodeoxyglucose positron emission tomography (FDG‐PET) in the detection of primary tumors in patients with cervical metastases from unknown primary tumors. METHODS Sixteen studies (involving a total of 302 patients) published between 1994 and 2003 were reviewed. These studies evaluated the role of FDG‐PET in the detection of unknown primary tumors after conventional workup. In all studies, conventional workup included either panendoscopy or computed tomographic/magnetic resonance imaging, and in 10 of 16 studies, both of these diagnostic techniques were performed before diagnosis. RESULTS The overall sensitivity, specificity, and accuracy rates of FDG‐PET in detecting unknown primary tumors were 88.3%, 74.9%, and 78.8%, respectively. Furthermore, FDG‐PET detected 24.5% of tumors that were not apparent after conventional workup. FDG‐PET imaging also led to the detection of previously unrecognized metastases in 27.1% of patients (regional, 15.9%; distant, 11.2%). FDG‐PET had notably low specificity and a high false‐positive rate (39.3%) in the tonsils. In contrast, the false‐positive rates for FDG‐PET of the base of tongue and hypopharynx were only 21.4% and 8.3%, respectively. FDG‐PET exhibited decreased sensitivity to tumors in the base of tongue (81.5%). The sensitivity of this technique at other sites was 90.5%. CONCLUSIONS FDG‐PET detected primary tumors that went undetected by other modalities in approximately 25% of cases and was sensitive in the detection of previously unrecognized regional or distant metastases in 27% of cases. FDG‐PET had low specificity for tonsillar tumors and low sensitivity for base‐of‐tongue malignancies. Cancer 2004. © 2004 American Cancer Society.