Fluorine-18 fluoro-2-deoxy-D-glucose (FDG) uptake in brown adipose tissue (BAT) may generate FDG-PET scan misinterpretation. Recent studies have shown reduced FDG uptake in BAT in rats treated with high doses of the beta-blocker propranolol. The aim of this observational study was to present a cohort of patients with high FDG uptake in BAT who underwent a second scan after receiving a low dose of propranolol, to determine whether the use of this premedication could improve the diagnostic confidence of FDG-PET scans by inhibition FDG uptake in BAT, and also whether administration of this drug affects tracer uptake in tumors.
Methods: Twenty-six cancer patients, presenting with increased BAT FDG uptake, were selected prospectively. On a different day, patients were given propranolol 20 mg orally 60 minutes prior to FDG administration 185-277.5 MBq (5-7.5 mCi) and were scanned again. Basal and postpropranolol BAT SUVmax, and tumor SUVmax (when present) were measured.
Results: Mean basal BAT SUVmax was 5.52+/-2.3. Mean postpropranolol SUVmax was 1.39+/-0.42 (P<0.0001). In 11 patients, the basal mean tumor SUVmax was 8.07+/-6.4, and 7.88+/-5.9 in postpropranolol scans (P=0.53). Nine patients showed mediastinal FDG uptake in the basal scan, affecting image interpretation. This was not observed in postpropranolol scans. No adverse effects due to propranolol were encountered.
Conclusions: In this patient cohort, there was significant reduction of FDG uptake in BAT following propranolol administration, allowing for adequate interpretation of FDG-PET and software-fused FDG-PET with CT images, particularly in the mediastinal area, without affecting tumor tracer uptake.