In 2008, more than 184,000 new patients were diagnosed with breast cancer, the most commonly diagnosed malignancy in women in the United States. Despite great advances over the past few years in screening, detection, and treatment, more than 40,000 women died from the disease in 2008.[1] Early breast cancer is considered a curable disease, but the curative potential of patients with locally advanced or metastatic disease is limited.
Imaging in Breast Cancer
Various imaging modalities have contributed to the evolution of breast cancer care. Early detection by mammography is a key element in the improvement of survival in breast cancer patients.[2] Ultrasonography is frequently used to differentiate benign cysts from solid lesions, and to assess axillary lymph node involvement. It also serves as a localizing imaging modality when biopsy is recommended.[3] Magnetic resonance imaging (MRI) of the breast yields better visualization of denser breasts and the chest wall, and is currently recommended for women who are at high risk for developing breast cancer (eg, those with a strong family history or known inherited susceptibility to the disease).[4]
PET Scan
In this review, we focus on the role of 2-[18F]-fluoro-2-deoxy-D-glucose (FDG)-PET in the diagnosis and management of breast cancer. FDG is a radioactive glucose analog with a short half-life. Tumor cells have a rapid growth rate and thus utilize more glucose. When a patient is injected with FDG, it is taken by these tumor cells, but not metabolized. The proportion of FDG trapping is dependent on the rate of glucose metabolism. The level of uptake is quantified and reported as a standardized uptake value (SUV).[5,6] FDG is given intravenously 1 hour before the scan in a very small dose, which has no pharmacologic effect. To avoid false-positives due to elevated blood glucose levels, the patient is asked to fast overnight and a normal blood glucose level must be documented.[7]
FDG-PET has the advantage of providing functional information compared with just the anatomic characterization provided by conventional imaging studies. FDG-PET is used for diagnostic staging, recurrence evaluation, and to assess response to therapy in multiple malignancies. A strong body of clinical evidence supports its use in non–small-cell lung cancer, Hodgkin and aggressive non-Hodgkin lymphoma, colorectal carcinoma, and melanoma.[8] Its role in advanced nonmetastatic, locally recurrent, and metastatic breast cancer will be discussed in this review.
PET/CT Fusion
Since 2005, PET/computed tomography (CT) fusion scanners have largely replaced traditional PET scans with the promise of better ability to detect cancer and lower false-positive rates. PET/CT fusion studies have the advantage of anatomic characterization in addition to the functional information provided by PET.[9,10] Furthermore, it would be less likely to mistake the normal physiologic accumulation seen in some PET studies when no corresponding lesion is observed on the CT portion.[11]
