 If you are found to be eligible to take part in this study, you will be randomly assigned as in the flip of a coin to 1 of 2 groups. Group 1 will take letrozole. Group 2 will take a placebo. A placebo is a substance that looks like the study drug but has no active ingredients. Neither the doctor nor you will know which group you will be in. However, if needed for your safety, the study staff and study doctor will be able to find out which group you are in. 