There is emerging data on the association of background parenchymal enhancement (BPE) on breast MRI with breast cancer risk. However, the underlying mechanism of BPE and its biologic relationship with cancer development remain unknown. Our study investigated the correlation of BPE with FDG PET standardized uptake values (SUV) in normal contralateral breast tissue of 35 women undergoing neoadjuvant chemotherapy. We found quantitative BPE area measures correlated with SUV metrics, and each decreased with therapy. Our findings suggest BPE reflects increased metabolic activity in normal breast tissue, which may provide valuable information for predicting cancer risk and response to therapy.