 In patients who are scheduled to undergo treatment with IVF for fertility preservation due to breast cancer, we would like to prospectively randomize them to fixed dose vs. titrated dose of Letrozole. Due to time restraints for chemotherapy patients may present for ovarian stimulation prior to Day 2 of their menstrual cycle. If this were to occur, Ganirelix may be started to suppress the pituitary hormones for down regulation prior to starting stimulation medications until day 2 of menstrual bleeding. Eligible subjects will be fully informed about the nature of the trial. Subjects could be enrolled for IVF treatment at any point after breast cancer diagnosis following surgery but before the initiation of chemotherapy, if chemotherapy has been prescribed by their oncologist. After obtaining written informed consent, the subjects will be screened based on inclusionexclusion criteria, medical and infertility history, Day 23 FSH and estradiol, physical and gynecological examination, oncology clearance and the Centers standard screening evaluations for IVF patients. A thorough gynecologic and endocrinologic evaluation will be performed before the start of any treatment. Laboratory assessments will include CBC, chemistry and lipid profile see attached history and physical form. Vital signs including blood pressure, pulse, and weight will be assessed at baseline prior to start of stimulation medication, with preoperative evaluation, on day of egg retrieval, and with post retrieval visits. 