The purpose of this study is to determine pathological response to a maximum of 18 weeks of neoadjuvant therapy using a combination of letrozole and Bevacizumab in post-menopausal women with pathologically confirmed invasive ductal cancer or invasive lobular cancer of the breast whose tumors are hormone positive.

This is an open label, single arm, and Phase II study of the combination of Letrozole and Bevacizumab in patients with newly diagnosed breast cancer. Patients meeting the eligibility criteria and who have signed the consent form will start Letrozole 2.5 mg by mouth a day and Bevacizumab 15 mg per Kg IV every 3 weeks for 18 weeks (24 weeks if still responding at week 18 if approved by the PI). After neoadjuvant therapy, participants will undergo surgical treatment and will receive adjuvant therapy according to the treating physician.

Inclusion Criteria:

• Pathologically confirmed invasive ductal carcinoma or invasive lobular carcinoma of the breast, T2-T4 / T4a-c / N0-2 / M0, with positive estrogen and/or progesterone receptors. Patients with inflammatory breast cancer will not be included (Stage IIIb). Patients previously treated patients with no measurable disease or patients with metastatic disease will be excluded.
• Written informed consent prior to study specific screening procedures, with the understanding that the patient has the right to withdraw from the study at any time, without prejudice (see Appendix B - consent form).
• Females 60 years of age (postmenopausal).
• Be ambulatory (outpatient) and have an ECOG PS <2 (Appendix F).
• Patients must have measurable disease by mammogram and/or breast ultrasound. The target lesion must not have been previously irradiated.
• No prior chemotherapy.
• Patients must have adequate organ and marrow function as defined as follows: absolute neutrophil count > 1,500/mm3, hemoglobin > 8.0 g/dl, platelets > 75,000/mm3, total bilirubin < 2 mg/dl, serum creatinine < 2 mg/dl, Transaminases (AST, ALT) may be up to 2.0 x institutional upper limit of normal. In addition < 1 gr of protein in 24 hr urine collection and urine protein/creatinine ratio < 1.0.
• No life threatening parenchymal disease or rapidly progressing disease warranting cytotoxic chemotherapy.
• Hypertension must be controlled (<150/100 mmHg).
• Ejection Fraction > 50%.
• No history of thrombosis during the previous year.

Exclusion Criteria:

• Current, recent (within 4 weeks of the first infusion of this study), or planned participation in an experimental drug study other than this sponsor-investigator Bevacizumab cancer study.
• Uncontrolled high blood pressure (150/100 mmHg)
• Unstable angina
• New York Heart Association (NYHA) Grade II or greater congestive heart failure see Appendix G)
• History of myocardial infarction within 6 months
• History of stroke within 6 months
• Clinically significant peripheral vascular disease
• History of a bleeding disorder
• Presence of central nervous system or brain metastases
• Major surgical procedure, open biopsy, or significant traumatic injury within 28 days prior to Day 0, anticipation of need for major surgical procedure during the course of the study
• Minor surgical procedures, fine needle aspirations or core biopsies within 7 days prior to Day 0
• Pregnant (positive pregnancy test) or lactating
• Urine protein: creatinine ratio 1.0 at screening. Patients demonstrating > 1 gr of protein in 24 hr urine collection within 4 weeks prior to study entry will not participate in the trial.
• History of abdominal fistula, gastrointestinal perforation, or intra-abdominal abscess within 6 months prior to Day 0
• Serious, non-healing wound, ulcer, or bone fracture
• Unwilling or unable to comply with the protocol for the duration of the study.
• Psychiatric illness/social situations that would limit compliance with study requirements.
• History of another malignancy within the last five years except cured basal cell carcinoma of skin and carcinoma in-situ of uterine cervix.
• Patients with metastatic disease.