Presurgical Treatment With Letrozole in Patients With Early-stage Breast Cancer.

Some tumors use estrogen in the body to assist with growth. Letrozole is a drug that is prevents cells from producing estrogens. This should assist with the slowing of growth of tumor cells. Letrozole also promotes cell destruction by inhibiting a cellular destruction pathway. The objectives of this study will look at the differences between the cellular destruction pathway before and after letrozole use, and the differences in the cellular destruction pathway in participants that have received letrozole versus those who did not. The study will also look at a gene in all participants called Ki67. This gene is associated with the rate of tumor cell growth. The study will measure the levels of Ki67 and compare them to the amount of activation of the cellular destruction pathway. Participants in this study will have undergone a diagnostic biopsy of their breast tissue. In order to meet these objectives, one group of participants (Arm A) will not receive letrozole. Tissue leftover from their diagnostic biopsy will be treated with everolimus (RAD001) in the laboratory and the effects of this drug on the cellular destruction pathway will be studied. The other group of participants (Arm B) will take letrozole for a minimum of 10 and maximum of 21 days. They will have a second tumor sample taken as part of their surgical procedure completed to remove the tumor tissue. Any differences in the cellular destruction pathway before and after exposure to letrozole will be measured.