Response to Therapy in Breast Cancer

Increasing numbers of patients with newly diagnosed breast cancer receive primary systemic therapy followed by surgery. Histopathology provides an accurate assessment of treatment efficacy on the basis of the extent of residual tumor and regres-sive changes within tumor tissue. However, only approximately 20 % of breast cancer patients achieve a pathologic complete response, a fact that necessitates methods for monitoring ther-apeutic effectiveness early during therapy. 18F-FDG PET and 18F-FDG PET/CT provide essential information regarding a re-sponse to primary chemotherapy. Patients with low tumor meta-bolic activity on pretreatment 18F-FDG PET are not likely to achieve a histopathologic response. The degree of changes in 18F-FDG uptake after the initiation of therapy is correlated with the histopathologic response after the completion of therapy. Thus, tumor metabolic changes assessed early during therap