Overview of the current status of PET in breast cancer imaging

Present limitations of available procedures for the diagnosis of breast cancer have stimulated the development of new methods based on Positron Emission Tomography (PET). PET can be used to evaluate primary lesions, regionally metastatic and systemic metastases of breast cancer by use of tracers including ¹⁵O-water ⁶²Cu PTSM [¹¹C]L-methionine, [¹⁸F]fluordeoxyglucose and [¹⁸F]fluoro-17-estradiol, for the assessment of blood flow, metabolism and receptor density. FDG-PET is an excellent clinical method to detect primary breast lesions over 1 cm in diameter and to characterize such lesions. Several reports have also indicated various degrees of sensitivity and specificity of PET-FDG in detecting axillar lymph nodes. However, the precise role of PET in staging breast cancer remains to be defined in careful prospective studies. Prospective evaluation of PET during breast cancer chemohormonotherapy demonstrated a decline in FDG uptake in patients responsive to treatment, while no significant decline in FDG uptake is seen in the non-responding patients examined post initiation of treatment. PET may be useful when used in combination with other techniques of morphological imaging, for the proper characterization of hypermetabolic tissue. Additional studies including large populations with known or suspected breast cancer will enhance the clinical role of this technique for solving difficult diagnostic questions.