¹⁸F-FDG PET/CT in brain metastases from an unknown primary

The aim is to evaluate the diagnostic value of 18F-fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET/CT) in the clinical management of patients presenting with brain metastasis of unknown primary origin (CUP). A total of 46 patients (26 males, 20 females) with diagnosis of brain metastasis according to histopathology and/or conventional imaging were enrolled into this retrospective study. Thirty-four patients (74%) were with histologically verified metastatic process, while in the rest 12 of them (26%) clinical suspicion was based on highly suspected imaging and clinical data. FDG PET/CT was able to identify primary localizations in 32 of 46 patients (70%), mostly lung carcinoma (75%). The most common extracranial metastatic lesions detected by PET/CT in patients with cerebral metastases from CUPs were: lymph nodes (61%), lung (28%) and bone (28%). The overall sensitivity, specificity and accuracy rates of the study were identified as 100%, 71% and 91%. In summary, the use of FDG PET/CT in patients with brain metastases from occult carcinoma could be used at an earlier stage due to its documented high sensitivity, specificity and accuracy, with exceptional high degree of detection of primary lesion in nearly three quarters of cases, most often lung carcinoma (75%). PET/CT successfully differentiates extracranial metastatic foci, as a generalized disease is observed in nearly half of the cases. Therefore, the correct distinction of oligometastatic disease from generalized dissemination process is essential for proper planning of therapeutic approach - locally aggressive or systemic. Keywords: FDG PET/CT. Brain metastasis. Unknown primary origin. (author)