- Patients who received tamoxifen or another selective estrogen receptor modulator (SERM) for the prevention or treatment of breast cancer or for other indications (e.g., osteoporosis, prior ductal carcinoma in situ (DCIS)), or who receive aromatase inhibitors for prevention or treatment of breast cancer, are eligible. Patients who are hormone-receptor positive and who have received other hormonal agents for the treatment of breast cancer (e.g., Fulvestrant®) are also eligible. Tamoxifen therapy or other hormonal agents should be discontinued at least 1 week before the patient is started on study therapy.