At present there is no clinical role for whole or half body imaging with 18F-fluoro-2-deoxy-D-glucose (FDG)–positron emission tomography (PET) in detecting breast cancer, but this technique has been shown to be useful in staging and restaging breast cancer, in the evaluation of response to therapy, and in problem solving when conventional imaging results are equivocal. In these scenarios FDG–PET often demonstrates loco-regional or unsuspected distant disease that affects clinical management.
Positron emission tomography
PET is an imaging technique increasingly used in oncology. It may map functional activity before structural changes have taken place. The most commonly used isotope is FDG, a glucose analogue which, like normal glucose, is taken up by cells via the membrane glucose transporter system and phosphorylated by hexokinase. Unlike glucose, the metabolic product FDG-6-phosphate does not cross the cell membrane and is trapped in cells. FDG accumulation is dependent on the rate of transport through the cell membrane mediated by glucose transporters (GLUT). Many malignancies, including breast cancers, show increased expression of GLUT-1, contributing to increased FDG accumulation. FDG may also accumulate in non-malignant areas of infection or inflammation leading to false-positive findings.
An intravenous injection of 300 to 400 megabecquerels (MBq) of FDG is used in most institutions and the patient imaged at least one hour after injection. Delaying the time of imaging may improve the tumor-to-background ratio.