Clinical evaluation of 18Fª²FDG PET imaging in detection of unknown primary tumors

    XU Haiª²Feng£¬ ZHOU Runª²Suo£¬ YUAN Mengª²Hui£¬ ZHANG Jinª²He£¬ WANG Lei£¬ ZHOU Feiª²Hua

    Department of Nuclear Medicine, Tangdu Hospital, Fourth Military Medical University, Xi¡¯an 710038, China

    ¡¾Abstract¡¿ AIM: To evaluate the value of whole body 2ª²18Fª²deoxyglucose positron emission tomography (FDG PET) imaging for the detection of the primary tumor in patients with metastases of unknown origin. METHODS: Whole body PET scans were performed in 39 patients with various metastases from unknown origin after unsuccessful conventional diagnostic procedures. The images were interpreted by visual inspection and semiª²quantitive analysis ( standardized uptake value, SUV). RESULTS: PET imaging found the primary foci in 25 patients, of which 24 were true positive and one case was false positive by further pathologic examination. The corresponding detection rate was 61.5% (24/39). Among the 24 primary foci of the tumor, 14 were in the lung, 1 in liver, 1 in stomach, 2 in pancreas, 3 in colorectum, 1 in nasopharynx, 2 in mediastinum and 1 in kidney. In addition to those found by other clinical imaging, 37 more metastatic foci of cancer patients were identified by PET imaging. In the 14/39 patients, FDG PET imaging did not reveal lesions suspected to be primary tumor. For 12 months¡¯ followª²up, the mortality rate was 29.0% (7/24) and 43.0% (6/14) respectively in patients with identified and unidentified primary tumor. CONCLUSION: Whole body 18Fª²FDG PET imaging is valuable in detecting the unknown primary tumors. PET imaging allows identification of the primary site and metastatic lesions in a single scan. It is also helpful in clinical stage setting, appropriate management selection and prognosis prediction for patients with metastases of unknown origin. ......