Medicines for Advanced Breast Cancer

Many different medicines are used to treat advanced breast cancer. Doctors determine the best medicine or combination of medicines based on several factors, including:

• The stage (extent) of the cancer
• The age and menopausal status of the person with cancer
• Previous treatments the person has received
• Whether the breast cancer is positive for hormone receptors and/or human epidermal growth factor receptor 2 (HER2)
• Possible side effects of the treatment

Medicines are a systemic treatment. This means they go throughout the body and treat the whole system, affecting cancer cells wherever they might be. There are different categories of drugs used to treat advanced breast cancer, including:^1,2

• Chemotherapy
• Hormone therapy
• Targeted therapy
• Immunotherapy

Chemotherapy

Chemotherapy drugs work by targeting rapidly dividing cells and damaging the DNA and/or RNA to stop the cells from growing. Chemotherapy drugs may be used in combination or as a single agent (monotherapy). In metastatic breast cancer, sequential single agents are usually recommended. This method uses 1 chemotherapy drug at a time, 1 after another. The drug is changed to another when the breast cancer no longer responds or begins growing, or the person can no longer tolerate the specific drug.^3,4

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 that bind to hormones like estrogen and progesterone. When these hormones connect to the cancer cells’ receptors, they can fuel the growth of the breast cancer. This causes it to grow and spread faster.⁵

There are different kinds of hormone therapy, including:⁶

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

Targeted therapy

Targeted therapy stops or slows breast cancer by interfering with specific areas of cancer cells that are involved in the cancer cells' growth processes, or by focusing on specific features that are unique to cancer cells. By focusing on specific features of cancer cells, targeted therapy aims to minimize damage to normal cells.^7,8

Many types of targeted therapy are used to treat certain early-stage, advanced, and/or metastatic breast cancers, including:^7,8

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

Immunotherapy

Immunotherapy is a type of systemic treatment that aims to boost a person's own immune system to fight cancer.⁹

Several types of immunotherapy are being studied or have already been approved to treat certain forms of breast cancer, including:⁹

• Monoclonal antibodies
• Adoptive cell transfer

What are the possible side effects of medicines for advanced breast cancer?

Side effects can vary depending on the specific drug you are taking. Not everyone who receives the same treatment 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:

• Hot flashes
• Headache
• Decreased sex drive (libido)
• Mood swings
• Changes to breast tissue (possible tenderness)
• Vaginal dryness
• Nausea

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

These are not all the possible side effects of medicines for advanced breast cancer. Talk to your doctor about what to expect or if you experience any changes that concern you during treatment.