Clinical applications of 18F-fluorodeoxyglucose positron emission tomography/computed tomography in carcinoma of unknown primary

Background Carcinoma of unknown primary (CUP) encompasses a heterogeneous group of tumors with varying clinical features. The management of patients of CUP remains a clinical challenge. The purpose of this study was to evaluate the clinical applications of integrated F-18-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) information in patients with CUP, including detecting the occult primary tumor and effecting on disease therapy. Methods One hundred and forty-nine patients with histologically-proven metastases of CUP were included. For all patients, the conventional diagnostic work-up was unsuccessful in localizing the primary site. Whole-body PET/CT images were obtained approximately 60 minutes after intravenous injection of 350-425 MBq of F-18-FDG. Results In 24.8% of patients, FDG PET/CT detected primary tumors that were not apparent after conventional workup. In this group of patients, the overall sensitivity, specificity, and accuracy rates of FDG PET/CT in detecting unknown primary tumors were 86.0%, 87.7%, and 87.2%, respectively. FDG PET/CT imaging also led to the detection of previously unrecognized metastases in 29.5% of patients. Forty-seven (31.5%, 47 of 149) patients underwent a change in therapeutic management. Conclusions FDG PET/CT is a valuable tool in patients with CUP, because it assisted in detecting unknown primary tumors and previously unrecognized distant metastases, and optimized the mangement of these patients. Chin Med J 2011;124(7):1010-1014