Abstract
Background and Purpose [18F]Fluoro-2-deoxy-2-d-glucose (FDG) positron emission tomography/computed tomography
(PET/CT) has a promising role in the workup and management of carcinoma of unknown
primary (CUP). We have evaluated the effect of whole-body FDG PET/CT in assessing
the patients presented with suspected brain metastasis (CUP-BM) on brain magnetic
resonance imaging (MRI) or computed tomography (CT).
Materials and Methods This retrospective study included FDG PET/CT of 50 patients (24 males, mean: 58 ± 12.2
years old) with a CUP-BM diagnosis based on MRI and CT imaging. The final diagnosis
of primary brain neoplasm (BP) or brain metastases (BM) was based on FDG PET/CT findings
and/or histopathology (HPE).
Results On FDG PET/CT, 52% (26/50) of patients did not have any systemic lesion apart from
a brain lesion. Out of these, 50% (13/26) had HPE confirmation of primary brain neoplasm
(BP). FDG PET/CT identified multiple systemic lesions apart from brain lesions in
the remaining 48% (24/50) of patients. They were categorized as the brain metastases
(BM) group. The primary lesions were located in the lungs (n = 20), kidneys (n = 1), prostate (n = 1), esophagus (n = 1), and tongue (n = 1).
Conclusion FDG PET/CT could suggest a diagnosis of BM based on the presence of systemic lesions.
It also provides an easily accessible peripheral site for biopsy and systemic disease
burden in a single scan. FDG PET/CT's up-front use in suspected CUP-BM on CT and/or
MRI could differentiate the BM from BP in most cases and avoid brain biopsy in the
BM group.
Keywords
FDG PET/CT - brain metastases - carcinoma of unknown primary
