Study Evaluating CCI-779 and Letrozole in Post-menopausal Women With Breast Cancer

In this clinical research study, postmenopausal subjects with metastatic breast cancer will be given either the combination of temsirolimus (CCI-779) and letrozole or a placebo and letrozole in first-line hormonal treatment. The primary endpoint of this study is to determine overall progression free survival. Individual subjects will participate in the active treatment phase of the study until disease progression or withdrawal of consent, provided that test article is being tolerated. All subjects will be asked to participate in the long-term follow-up phase of the study, which includes follow-up every 3 months until disease progression (for subjects who withdraw for reasons other than documented progressive disease) or until any new cancer treatment is received, and for survival. The estimated duration of study participation is 34 months.