NSABP- B33

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Currently, patients whose primary breast cancer demonstrated estrogen receptors, receive five years of anti-estrogen treatment with tamoxifen. This has been standard care for many years. There is no data supporting more than five years of tamoxifen use, in fact at least one study showed worse results with more than five years of tamoxifen. There is no treatment offered to patients beyond this other than close observation. Exemestane is a new aromatase inhibitor, i.e. a drug that interferes with the metabolism of steroid hormones. The primary aim of this randomized, placebo-controlled, double-blind clinical trial is to determine whether oral administration of exemestane, for 2 years, in postmenopausal patients with estrogen-receptor-positive (ER+) and/or progesterone-receptor-positive (PgR+) breast cancer (CT 1-3 cNO-1 MO) who have completed 5 years of tamoxifen therapy, will prolong disease-free survival and overall survival when compared with placebo. To be eligible, patients must have completed approximately 5 years of adjuvant tamoxifen therapy (either 10 mg po twice a day or 20 mg po daily), be disease free, and have been resected by lumpectomy and axillary node dissection or by modified radical mastectomy. Eligible patients may have received either adjuvant or neoadjuvant chemotherapy at the time of their breast cancer diagnosis. Following stratification by nodal status, patients will be randomized to receive either exemestane 25 mg po daily or placebo, for 2 years. Another aim of this study is to evaluate the effect of tamoxifen withdrawal on bone and to determine if exemestane has any additional effects on the rate of bone loss resulting from tamoxifen withdrawal. Data for fractures, height, and total serum alkaline phosphatase will be collected on the entire study population. A subgroup of 216 patients entered in the trial will be prospectively evaluated using serial measurements of both bone mineral density (BMD) and bone biochemical markers. Specific NSABP sites will be asked to participate in this bone mineral density (BBL) substudy (see Appendix A). (UConn was not chosen to participate in the BBL substudy).