International Journal of Nuclear Medicine Research  (Volume 3 Issue 2)
 Impact of 18F-FDG PET/CT for Detecting Primary Tumor Focus in Patients with Histopathologically Proven Metastasis Nuclear
Pages 56-62

Elgin Ozkan, Cigdem Soydal, Mine Araz and N. Ozlem Kucuk


Published: 14 October 2016


Purpose: To describe the impact of fluorine (18F) - fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) in detecting primary tumor focus in our patient population who had histopathologically proven metastasis.

Methods:37 patients who underwent 18F-FDG PET/CT to detect primary tumor focus in our department were included in the study. The results of PET/CT and clinical follow-up data were reviewed retrospectively. PET/CT results were compared with histological analysis and/or clinical follow-up data.

Results:Primary site of malignancy was correctly identified by PET/CT in 16 patients (16/37, 43%). Lung was the most common detected site (7/16). The mean SUV of metastatic tumor was higher than that of primary tumor. False positive and false negative results were obtained in 2 patients, respectively. In the remaining patients (17/37; 46%) the primary tumor was not localized by PET/CT. According to these results, the sensitivity and specificity of PET/CT were calculated as 89% and 90%, respectively. However, PET/CT scan determined additional metastatic focus and therapy management was changed (9/37, 24%). The primary focus was established in 4 of 8 (50%) patients with metastatic cervical adenopathy and in 12 of 29 (41%) patients with extra cervical metastases.

Conclusions:18F-FDG PET/CT can detect the primary tumor focus in about half of all patients with histopathologically proven metastases. In the remaining patients, it may contribute to therapy management by identifying additional foci.
 Cancer of unknown primary, 18F-FDG, Positron emission tomography, Therapy management, Metastases.