This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This protocol is designed to evaluate the relationship between [18F]FLT uptake parameters and pathologic complete response to chemotherapy of the primary tumor in patients with locally advanced breast cancer. The protocol aims include: To evaluate the relationship between [18F]FLT uptake parameters and the clinical anatomical (CT) and metabolic (FDG PET uptake) response To compare the utility of [18F]FLT and [18F]FDG uptake parameters for predicting early treatment response (response assessment prior to completion of therapy) in patients with locally advanced breast cancer. To demonstrate correlation between [18F]FLT uptake parameters and tumor proliferation markers in breast cancer To continue to monitor for potential safety issues and define any physiologic effects associated with [18F] fluorothymidine (FLT) administration