Several publications have addressed the role of PET imaging for biological characterization of breast cancer. A modest but significant correlation was reported between tumor grading and FDG uptake. Few studies reported a positive correlation between SUV and the Ki-67 labeling index of malignant breast tumors. Others have correlated p53 expression in breast cancer and FDG uptake. F18-Fluoro-3'-deoxythymidine (FLT) has been developed as a PET marker for cellular proliferation has been developed for imaging cell proliferation and findings correlate strongly with the Ki-67 labeling index in breast cancer. A 10-minute FLT-PET scan acquired two weeks after the end of the first course of chemotherapy, has been shown in two recent studies to be useful for predicting longer-term efficacy of chemotherapy regimens for women with breast cancer.