Low positive yield from routine inclusion of the brain in whole-body 18F-FDG PET/CT imaging for noncerebral malignancies: results from a large population study.

OBJECTIVE: This retrospective study was conducted to assess the incremental value, if any, of including the brain in whole-body fluorine-18 fluorodeoxyglucose (F-FDG) positron emission tomography/computed tomography (PET/CT) studies in patients with extracalvarial primary malignancies.
METHODS: The scan data of 5110 F-FDG PET/CT studies conducted from March 2009 to December 2011 were reviewed.
RESULTS: Abnormal brain lesions were detected in 76/5110 patients who had undergone F-FDG PET/CT studies. Among them, 16 patients had lesions with F-FDG uptake less than that of the surrounding background and 54 had lesions with increased F-FDG uptake. Six patients had neither increased nor decreased tracer uptake in their brain lesions (identified on the CT component of the study). In the first group of patients, infarct was seen in four patients, treated brain metastases were seen in eight (five surgical and three through external beam radiotherapy), and untreated metastases were seen in four patients. In the 54 patients with increased uptake, metastatic lesions were identified in 51 and central nervous system involvement by systemic lymphoma in three. The third group showed metastases in four patients and central nervous system involvement by systemic lymphoma in one; one patient was lost to follow-up without a final diagnosis. Out of 63 patients with untreated cerebral metastases detected on the F-FDG PET/CT study, cerebral metastases were unknown before F-FDG PET/CT in 40 patients. Of these 40 patients, the brain was the only site of metastatic involvement in eight patients.
CONCLUSION: Inclusion of the brain routinely in whole-body F-FDG PET/CT studies detected previously unknown metastases in only 0.7% (40/5110) of studies, with negligible impact (0.15%) on staging.