This randomized phase III trial studies tamoxifen citrate or letrozole together with bevacizumab to see how well it works compared with tamoxifen citrate or letrozole alone in treating women with stage IIIB or stage IV breast cancer. Estrogen can cause the growth of breast cancer cells. Hormone therapy using tamoxifen citrate or letrozole may fight breast cancer by blocking the use of estrogen by the tumor cells. Immunotherapy with monoclonal antibodies, such as bevacizumab, may induce changes in the body's immune system and may interfere with the ability of tumor cells to grow and spread. It is not yet known whether giving hormone therapy is more effective with or without bevacizumab in treating advanced breast cancer.

PRIMARY OBJECTIVES:

I. To compare the progression-free survival of letrozole therapy alone with the combination of letrozole therapy plus bevacizumab as first-line treatment in women with estrogen- and/or progesterone-receptor-positive advanced breast cancer.

SECONDARY OBJECTIVES:

I. To compare the proportion of patients receiving letrozole alone, who remain progression-free at 6 and 12 months, to those receiving letrozole plus bevacizumab.

II. To compare the incidence of objective response (complete response [CR] + partial response [PR]) in patients receiving letrozole with and without bevacizumab, as determined by Response Evaluation Criteria in Solid Tumors (RECIST) criteria, excluding patients with non-measurable disease.

III. To compare the incidence of clinical benefit (CR + PR + stable disease >= 6 months) in patients receiving letrozole with and without bevacizumab.

IV. To compare the duration of objective response in patients receiving letrozole with and without bevacizumab.

V. To compare the time to treatment failure in patients receiving letrozole with and without bevacizumab.

VI. To compare the overall survival of patients receiving letrozole with and without bevacizumab, including the probability of survival until 36 months.

VII. To compare toxicity levels between the bevacizumab arm and the arm without bevacizumab in both the letrozole-treated patients and in the tamoxifen-treated patients.

VIII. To compare progression-free survival and overall survival of all patients receiving endocrine therapy with and without bevacizumab (by combining both letrozole and tamoxifen* patient subgroups).

CORRELATIVE OBJECTIVES:

I. To compare baseline and changes in serial levels of circulating endothelial cells and circulating tumor cells in patients treated with endocrine therapy alone or endocrine therapy plus bevacizumab, and to explore the relationship of these markers with progression free survival.

II. To conduct proteomic analysis of longitudinal samples from patients with advanced-stage disease undergoing hormonal therapy to define new serum-based biomarkers related to disease activity.

III. To identify biologic correlates that will predict progression-free survival (PFS) and response to therapy.

IV. To conduct pharmacogenomic assessment of candidate variants in the VEGF, CYP2D6, and CYP19 genes and evaluate their association with PFS and other study outcomes.

V. To identify single nucleotide polymorphisms (SNPs) associated with progression free survival in the genome-wide approach (GWAS).

VI. To identify factors other than chronological age that predict the risk of grade 3, 4 or 5 toxicity with bevacizumab and endocrine therapy by means of functional age assessment measures.

VII. To perform an exploratory analysis of the ability of the other factors included in the functional age assessment (either individual or in combination), to predict the risk of grade 3, 4 or 5 toxicity.

VIII. To evaluate longitudinal changes in the parameters of the factors described in objective VI while on therapy.

OUTLINE: Patients are randomized to 1 of 2 treatment arms.

NOTE: The placebo-controlled portion of the study was canceled on 5-15-10.

ARM I: Patients receive endocrine therapy* (tamoxifen citrate or letrozole) orally (PO) once daily (QD) on days 1-21 and bevacizumab intravenously (IV) over 30-90 minutes on day 1. Treatment repeats every 21 days in the absence of disease progression or unacceptable toxicity.

ARM II: Patients receive endocrine therapy* (tamoxifen citrate or letrozole) PO QD on days 1-21. Treatment repeats every 21 days in the absence of disease progression or unacceptable toxicity.

After completion of study therapy, patients are followed up every 6 months for the first 2 years and then annually for up to 3 years.

* NOTE: As of 5/15/2011, patients only receive letrozole.

Inclusion Criteria:

• Histologic confirmation of invasive cancer of the female breast in either the primary or metastatic setting

  • Stage IV disease or stage IIIB disease (using American Joint Committee on Cancer [AJCC] criteria, 6th edition) not amenable to local therapy

• Patients may not have a "currently active" second malignancy other than non-melanoma skin cancers; patients are not considered to have a "currently active" malignancy if they have completed therapy and are considered by their physician to be at less than 30% risk of relapse

• Tumors (from either primary or metastatic sites) must express estrogen receptor (ER) and/or progesterone receptor (PgR) in >= 1% of cells will be considered positive

• Postmenopausal women are eligible for this trial; before study registration, menopausal status must be defined according to the criteria below:

  • Age >= 55 years and one year or more of amenorrhea
  • Age < 55 years and one year or more of amenorrhea, with an estradiol assay < 20 pg/ml
  • For women age < 55 with prior hysterectomy but intact ovaries, with an estradiol assay < 20 pg/ml
  • Surgical menopause with bilateral oophorectomy (at least 28 days must elapse from surgery to time of study registration)
  • Ovarian suppression on a luteinizing hormone-releasing hormone (LH-RH) agonist

• Premenopausal women who do not meet the postmenopausal criteria above are also eligible, but are required to undergo ovarian suppression; this can be initiated any time prior to or on day 1 of protocol therapy, regardless of chosen endocrine therapy, and will continue for the duration of protocol therapy

• Patients must have measurable or non-measurable disease by RECIST criteria, with radiologic scans within 28 days of study registration

  • Measurable disease: lesions that can be accurately measured in at least one dimension (longest diameter to be recorded) as >= 2.0 cm with conventional techniques or as >= 1.0 cm with spiral computed tomography (CT) scan

  • Non-measurable disease: all other lesions, including small lesions (longest diameter < 2.0 cm with conventional techniques or < 1.0 cm with spiral CT scan) and truly non-measurable lesions

  • Lesions that are considered non-measurable include the following:

    • Bone lesions
    • Leptomeningeal disease
    • Ascites
    • Pleural/pericardial effusion
    • Inflammatory breast disease
    • Abdominal masses that are not confirmed and followed by imaging techniques
    • Cystic lesions

• Prior endocrine therapy is not required

  • Prior endocrine therapy in the metastatic setting is not permitted (unless tamoxifen or an aromatase inhibitor was initiated within 4 weeks prior to registration to facilitate enrollment of patients who recently started first-line endocrine therapy for metastatic breast cancer); if prior letrozole therapy was initiated within the past 4 weeks, the patients should remain on letrozole as the study therapy; patients who began therapy with tamoxifen, anastrozole or exemestane must switch to letrozole to be eligible to participate in this study
  • Prior endocrine therapy in the adjuvant setting is permitted; there is no time restriction for how long the patient must be on the adjuvant endocrine therapy, nor is there a time restriction for how long the patient needs to be off prior adjuvant endocrine therapy before beginning protocol therapy on 40503
  • Prior treatment with ovarian suppression is allowed in either the adjuvant or metastatic setting; if medical ovarian suppression is being administered it can be initiated any time prior to or at the start of protocol therapy, and continued throughout the duration of the trial; surgical castration with bilateral oophorectomy must be performed at least 28 days prior to study registration (due to concerns of poor wound healing on bevacizumab)

• Patients may not have received any prior anti-VEGF or VEGFR tyrosine kinase inhibitor therapy

• Prior radiotherapy must have been completed and all toxicities resolved at least two weeks prior to registration

• Chemotherapy in the adjuvant or neoadjuvant setting is permitted; at least twelve months prior to registration must have elapsed since the completion of adjuvant or neoadjuvant chemotherapy and all toxicities must have resolved; taxane-related neurotoxicity must have resolved to sensory grade < 2 and no motor neuropathy of any grade is allowed

• Patients may have received one prior chemotherapy regimen for metastatic disease; the final dose of prior chemotherapy must have been administered at least 3 weeks prior to study registration

• Treatment with bisphosphonates is allowed and recommended as per American Society of Clinical Oncology (ASCO) guidelines

• Patients must not have had a major surgical procedure, open biopsy, or significant traumatic injury within 28 days prior to study registration, and must have fully recovered from any such procedure

• Patients must not have anticipation of need for major surgical procedure during the course of the study

• Patients must not have had a core biopsy or other minor surgical procedure, within 7 days prior to study registration; placement of a vascular access device is allowed within 7 days of registration

• Patients must not have a history of abdominal fistula, or intra-abdominal abscess within 6 months prior to study registration

• Patients with a history of gastrointestinal (GI) perforation within 12 months prior to registration are not eligible

• Patients with a history of significant bleeding episodes (e.g., hemoptysis, upper or lower GI bleeding) within 6 months prior to registration are not eligible

• Patients must not have clinically significant cardiovascular disease that includes the following:

  • Uncontrolled hypertension defined as systolic blood pressure > 150 and/or diastolic blood pressure > 90 mmHg on antihypertensive medications or any prior history of hypertensive crisis or hypertensive encephalopathy
  • History of myocardial infarction or unstable angina within past 6 months
  • New York Heart Association (NYHA) grade 2 or greater congestive heart failure
  • Symptomatic peripheral vascular disease
  • Significant vascular disease (e.g., aortic aneurysm, aortic dissection) or arterial thrombotic events

• Full dose anticoagulation therapy is allowed for the treatment of prior conditions such as venous thrombosis or atrial fibrillation, but not for the treatment of prior arterial thrombotic events; patients on full dose anticoagulants must be on a stable dose of warfarin and have an in-range international normalized ratio (INR) (usually between 2 and 3) or be on a stable dose of low-molecular weight (LMW) heparin; patients receiving antiplatelet agents are eligible, as are patients on daily prophylactic aspirin or anticoagulation for atrial fibrillation

• Patients may not have a history of stroke or transient ischemic attack within 6 months prior to study registration

• Patients with a history of seizures must be well controlled with standard medication

• Patients must not have known central nervous system (CNS) metastases or leptomeningeal disease (screening with brain imaging is not required for asymptomatic patients)

• In aromatase inhibitor (AI)-treated patients: no known allergies to imidazole drugs, (e.g. clotrimazole, ketoconazole, miconazole, econazole, sulconazole, tioconazole, or terconazole) or compounds structurally similar to bevacizumab

• In tamoxifen treated patients: no known allergies to selective estrogen receptor modulators (e.g. tamoxifen, raloxifene or toremifene) or compounds structurally similar to bevacizumab; for patients enrolled after Update #5, endocrine therapy will consist of letrozole only and this criterion will no longer apply

• Eastern Cooperative Oncology Group (ECOG) (Zubrod) performance status =< 1

• No serious, non-healing wound, ulcer, or bone fracture

• Life expectancy of >= 12 weeks

• All patients who are premenopausal (if not already receiving ovarian suppression therapy/surgical oophorectomy) must have a negative beta-human chorionic gonadotropin (beta-Hcg) prior to starting on study treatment; patients may not be pregnant or nursing at any time during the study; ovarian suppression is required in women of childbearing potential by the start of protocol therapy, and will continue for the duration of protocol therapy

• Granulocytes >= 1,000/ul

• Platelet count >= 100,000/ul

• Creatinine =< 2.0 mg/dL

• Bilirubin =< 1.5 times upper limit of normal (ULN) unless due to Gilbert's syndrome

• Transaminases (alanine aminotransferase [ALT], aspartate aminotransferase [AST]) =< 2.5 times ULN

• International normalized ratio (INR) =< 1.6, unless on full dose warfarin

• Beta-Hcg negative in premenopausal women

• Urine protein =< 1+ or urine to plasma creatinine (UPC) < 1

  • Patients discovered to have >= 2+ proteinuria at baseline must undergo a 24-hour urine collection that must demonstrate < 1 g of protein/24 hr, or UPC ratio < 1 to allow participation in the study