Is there any incremental value of including brain in the field of view in oncological FDG PET/CT studies in patients with extra-cerebral primary malignancies?

Objectives This retrospective analysis was carried out to evaluate if there is any incremental value of including brain in FDG PET/CT studies in patients with extra-calvarial primary malignancies.

Methods Data of 5703 FDG PET/CT studies conducted from April 2009 to December 2011 and correlative brain imaging were reviewed. All studies were conducted in 3-D mode and diagnostic quality CT images with or without contrast, 60 min after intravenous injection of 8-10 mCi of F-18 FDG.

Results Abnormal brain lesions were detected in 86/5703 patients with 59 lesions showing increased FDG uptake and 13 lesions having reduced FDG uptake. Remaining 14 patients had neither increased nor decreased FDG uptake (small lesions <1 cm identified on CT component of the study). Of the 13 patients with reduced FDG uptake, 3 patients had infarct and treated brain metastases in 10 patients (5 surgery, 3 with EBRT and 2 patients with untreated metastases). 59 patients with increased uptake were metastatic lesions in 55 patients and CNS lymphoma in 4 cases. In 14 patients with no FDG uptake in lesions one patient was diagnosed to have infarct and one was found to have meningioma and rest 12 had metastases. Over all FDG PET detected viable malignant brain lesions in 59/73 (81%) patients and FDG PET/CT detected malignant lesions in 71/73 (97.2%) patients. Of these 73 patients brain lesions were unknown prior to FDG PET/CT study in 40 patients. Detection of these brain lesions lead to management change in only 9/40 patients. Over all unknown cerebral metastatic lesions were found in only 40/5703 (0.7%) studies conducted and this leads to change in treatment plan in only 9/5703 in 0.15%.

Conclusions Our results suggest that inclusion of brain routinely in F-18 FDG PET/CT studies might detect unknown metastases in only 0.7% studies and also the impact on management seems to be very little (0.15%)