title: Role of fluorodeoxyglucose-PET versus fluorodeoxyglucose-PET/computed tomography in detection of unknown primary tumor: a meta-analysis of the literature.
abstract: The objectives of this study were to evaluate the diagnostic accuracy of fluorodeoxyglucose (FDG)-PET and FDG-PET/computed tomography (CT) in the detection of primary tumors in patients presenting with carcinoma of unknown primary (CUP) unidentified by conventional workup, and to compare the statistical difference between the FDG-PET and FDG-PET/CT. Twenty-eight studies (involving a total of 910 patients) published between 1990 and 2007 were reviewed. These studies evaluated the role of FDG-PET and FDG-PET/CT in the detection of unknown primary tumors after physical examination and conventional workup failed to detect a primary tumor. Systematic methods were used to identify, select, and evaluate the methodological quality of the studies as well as to summarize the overall findings of sensitivity, specificity, and detection capacity of the primary tumor. The overall sensitivity and specificity of FDG-PET in detecting unknown primary tumors were 0.78 [95% confidence interval (CI): 0.72-0.84)] and 0.79 (95% CI: 0.74-0.83), respectively. Furthermore, FDG-PET detected 28.54% of tumors that were not apparent after CUP failed to be detected by conventional workup. Data were collected on the locations of primary tumors detected by FDG-PET in 17 studies and detected by FDG-PET/CT in seven studies. Tumors from the base of the tongue accounted for 20.7% (six of 29) of all false-positive FDG-PET scans, corresponding to a false-positive rate of 28.6% (six of 29), much higher than tumors from the others. FDG-PET exhibited a lower sensitivity with respect to the tumors at the base of the tongue and tonsils, which was 68.2 and 76.7%, respectively. In the eight studies with 430 patients diagnosed with CUP by FDG-PET/CT, 31.4% (n=135) of primary tumors were detected. The pooled sensitivity and specificity were 0.81 (95% CI: 0.74-0.87) and 0.83 (95% CI: 0.78-0.87), respectively. FDG-PET and FDG-PET/CT can detect primary tumors that went undetected by physical examination and conventional workup. FDG-PET exhibited lower sensitivity with respect to the tumors at the base of the tongue and the tonsils.
authors.affiliation: PET Center, The First Affiliated Hospital, College of Medicine, Zhejiang University, Zhejiang, China. mengjiedong@126.com
authors.forename: Meng-jie
authors.initials: MJ
authors.lastname: Dong
authors.forename: Kui
authors.initials: K
authors.lastname: Zhao
authors.forename: Xiang-tong
authors.initials: XT
authors.lastname: Lin
authors.forename: Jun
authors.initials: J
authors.lastname: Zhao
authors.forename: Ling-xiang
authors.initials: LX
authors.lastname: Ruan
authors.forename: Zhen-feng
authors.initials: ZF
authors.lastname: Liu
mesh_terms: D016206:Databases, Bibliographic; D005189:False Positive Reactions; D019788:Fluorodeoxyglucose F18 / Q000494:pharmacology*; D006801:Humans; D008495:Medical Oncology / Q000379:methods; D009369:Neoplasms / Q000175:diagnosis*; D049268:Positron-Emission Tomography / Q000295:instrumentation / Q000379:methods*; D012372:ROC Curve; D019275:Radiopharmaceuticals / Q000494:pharmacology*; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18