There are many different medications which may be used to treat advanced breast cancer. Doctors determine the best medication or combination of medications based on several criteria, including the stage (extent) of the cancer, the age and menopausal status of the patient, previous treatments the patient has received, whether the breast cancer is positive for hormone receptors and/or human epidermal growth factor receptor 2 (HER2), and possible side effects of the treatment.

Medications are a systemic treatment, meaning they go throughout the body and treat the whole system, affecting cancer cells wherever they might be. There are different categories of medications used to treat advanced breast cancer, including1,2:


Chemotherapy drugs work by targeting rapidly dividing cells and damaging the DNA and/or RNA to stop the cells from growing. Chemotherapy medications may be used in combination or as a single agent (called monotherapy).3 In metastatic breast cancer, sequential single agents are usually recommended. This method uses one chemotherapy drug at a time, one after another, and the drug is changed to another when the breast cancer no longer responds or begins growing, or the patient can no longer tolerate the specific drug.4

Hormone therapy

Hormone therapy is used to treat breast cancers that are hormone receptor-positive (HR+). HR+ breast cancers have receptors on the surface of their cells which bind to hormones in the body like estrogen and progesterone. When these hormones connect to the cancer cells’ receptors, it can fuel the growth of the breast cancer, causing it to grow and spread faster.5
There are different kinds of hormone therapy, including6:

  • Anti-estrogens
  • Aromatase inhibitors
  • Gonadotropin releasing hormone agonists
  • Luteinizing hormone releasing hormone (LHRH) agonist

Targeted therapy

Targeted therapy stops or slows breast cancer by interfering with specific areas of cancer cells that are involved in the cancer cell’s growth processes. By focusing on specific features of cancer cells, targeted therapy aims to provide treatment for cancer that helps minimize damage to normal cells and causes fewer side effects.7,8

There are various types of targeted therapy that are used for the treatment of certain early-stage, advanced, and/or metastatic breast cancers, including:

  • HER2-targeting agents
  • CDK4/6 inhibitors
  • PARP inhibitors
  • mTOR inhibitors
  • PI3K inhibitors
  • Antibody-drug conjugates


Immunotherapy is a type of systemic treatment (treating the whole body) that aims to boost the individual’s own immune system to fight cancer. Immunotherapies are a type of biologic therapy, as they are made from substances produced from organisms that are alive. There are several types of immunotherapy that are currently being studied or are approved for the treatment of advanced breast cancer, including9:

  • Monoclonal antibodies
  • Adoptive cell transfer

Possible side effects

All medications can cause unwanted side effects. The possible side effects are specific to each medication type, and not everyone who receives the same treatment necessarily experiences the same side effects.3,6,8

Common side effects of chemotherapy include:

  • Nausea
  • Vomiting
  • Hair loss or thinning
  • Mouth sores
  • Fatigue
  • Decreased blood cells, which can potentially increase the risk of infection, bleeding, or anemia

Common side effects of hormone therapy include:

Common side effects of targeted therapy include:

  • Diarrhea
  • Fatigue
  • Skin or nail problems, including rashes or discoloration of nails
  • Reductions in the number of red blood cells, white blood cells, and/or platelets

This is not an exhaustive list of all side effects. Patients should talk to their doctor about their specific medications and what side effects they might experience.

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Written by: Emily Downward | Last reviewed: October 2020.