Abstract

Positron emission tomography (PET) is a metabolic radionuclide imaging method in which a tracer labeled with a positron emitter is detected with a dedicated system. 18F-fluorodeoxyglucose (FDG) accumulates in tumor cells because of their increased glycolytic activity, and is thus widely used as a tracer in oncology.

This increased metabolic activity precedes morphologic modifications, making FDG-PET a very useful tool for detecting and staging cancer.

It can also be used to characterize morphologic changes, differentiating not only between benign and malignant lesions, but also between viable tumor cells and areas of necrosis and/or fibrosis induced by treatments. Being a whole-body examination, it allows malignancies to be staged in a single procedure.

Systems combining PET and CT (computed tomography) offer improved performance, providing both metabolic and anatomical data.

This technique appears to be useful for initial breast cancer staging, especially of locally advanced forms and suspected recurrences (increase of isolated tumor marker). Early studies of PET evaluation of responses to hormonal and/or cytotoxic therapies have also given very promising results.

However, this technique does not seem sufficiently sensitive to be included in the initial screening or diagnosis of primary tumors, owing to its limited resolution (about 5 mm) and its restricted availability.

This approach is poorly sensitive when used for axillary assessment, but offers good specificity.