Inclusion Criteria

• Histopathologically confirmed breast cancer
• Documented Stage IV disease
• Estrogen and/or progesterone-receptor positive
• Stable disease on aromatase inhibitor or Faslodex® treatment begun at least 12 weeks prior to enrolment
• Performance status, ECOG = 0 or 1
• Life expectancy > 12 weeks
• History of freedom from progression for at least 6 months following surgery with a curative intent or for at least 6 months during adjuvant chemotherapy, adjuvant radiotherapy or adjuvant hormonal therapy such as tamoxifen/toremifene treatment
• No radiotherapy or major surgery within 4 weeks prior to enrolment

Exclusion Criteria

• Pregnant or lactating
• Known brain metastasis
• Bone marrow involvement as the only site of metastasis
• First line chemotherapy for Stage IV disease
• Past or current cancer other than breast cancer, except for curatively treated basal cell cancer or in situ cancer of the cervix with no evidence of disease
• Autoimmune disease, e. g., type I juvenile onset diabetes mellitus, antibody positive rheumatoid arthritis, Grave's disease, lupus, Crohn's disease, IBD, Hashimoto's thyroiditis
• Known intercurrent infections (including HBV or HCV) or immunosuppression [human immunodeficiency virus (HIV) or other conditions] or clinical evidence of these conditions
• Other significant active infection
• Pleural effusions and/or ascites requiring paracentesis every 2 weeks or more frequently
• Splenectomy
• Concurrent treatment with chemotherapeutic agents other than low-dose cyclophosphamide used in this study
• Treatment with interferons (IFNs), cytokines, systemic steroids or other biologicals within 4 weeks prior to enrolment
• Receipt of another investigational drug within 30 days of enrolment
• Known allergy to shellfish
• Known allergy to soy beans or soy products
• Known hypersensitivity to polysorbate 80
• Known hypersensitivity to the study drugs
• Legal incapacity or limited legal capacity