Registration:

The main purpose of this part of the study is to increase the number of postmenopausal women who have received the hormonal therapy drug letrozole as part of their adjuvant hormonal therapy for breast cancer treatment.  The women who complete their initial adjuvant hormonal therapy on this program will then be asked to take part in the National Surgical Adjuvant Breast and Bowel Project (NSABP) B-42 research study.  If you join this program you will be provided letrozole to complete 5 years of adjuvant hormonal therapy.  Once you have finished a total of 5 years of adjuvant hormonal therapy (including what you have already received before you join this program), you will then be asked if you would like to participate in a research study being conducted by the NSABP called B-42.  If you decide to participate in this Registration Program, you will not be required to participate in the B-42 study when you complete 5 years of adjuvant hormonal therapy.  The decision to take part in the B-42 study will be entirely up to you at that time.

B-42 Study:

The main purpose of this part of the study is to learn if receiving additional treatment after completing standard therapy will further reduce the chances of breast cancer returning.  You will receive letrozole or placebo for 5 years.  After your treatment on this study is over, your medical condition will continue to be followed indefinitely.