Chemotherapy medications circulate throughout the body and kill cancer cells by interfering with their ability to reproduce.
Typically, chemotherapy is given for approximately 3 to 6 months. The treatments are given by vein (IV) as an outpatient. Some treatments include daily pills as well as the IV treatments. Most treatments are given once every 2 or 3 weeks. Some treatments are given weekly. Many patients are able to function fairly normally between treatments, including being able to go to work and care for their families.
Side effects of chemotherapy vary depending on the drug, the dose, the combination, and the schedule in which they are given. In general, these drugs can cause varying degrees of nausea, vomiting, low blood counts, tingling of the fingers and toes – known as neuropathy – and the weakening of heart muscle.
If chemotherapy treatments are recommended, other medications may also be prescribed to support the body as it responds to the chemotherapy and cancer cells are killed. Many different kinds of drugs can be given to prevent or help minimize specific side effects. For example, if a chemotherapy drug is known to cause nausea and vomiting, anti-nausea drugs may be given. Patients may receive agents called colony-stimulating factors to increase the production of certain blood cells; and granulocyte colony-stimulating factor (G-CSF) which can stimulate the body to produce infection-fighting white blood cells.
Biologic therapies target specific proteins or molecular pathways that breast cancer cells use to grow. Trastuzumab (Herceptin) is a monoclonal antibody that halts the growth of breast cancer cells by binding to the her2neu protein on cancer cells. If the breast cancer is “HER2 positive,” this medication or other anti-HER2 medications may be offered to help prevent cancer recurrence. Trastuzumab is given intravenously. It works best when combined with standard chemotherapy for a number of months followed by a “maintenance” treatment of IV trastuzumab given every 3 weeks and continuing for one year of total therapy.
Patients who receive anti-HER2 therapy will often be monitored with an echocardiogram before starting the medication and periodically during the treatment period as there is a small risk that anti-HER2 therapy may damage the heart muscle. This is rare, and usually reversible.
Newer biologic agents that target HER2 include pertuzumab (Perjeta), lapatinib (Tykerb) and trastuzumab emtansine (T-DM1 or Kadcyla).
Drugs that stimulate a person’s own immune system to recognize and destroy breast cancer cells are known as immunotherapy. Also known as “checkpoint inhibitors,” these drugs interfere with protein signals that cancer cells use to grow and multiply. PDL-1 inhibitors are one category. Immunotherapy is usually given intravenously.
Anti-hormone therapy or endocrine therapy is often used to treat breast cancer. Breast cancer cells that have estrogen and progesterone receptors on the surface of the cells are known as estrogen and progesterone receptor-positive cancers. Similar to chemotherapy, this form of therapy can be used to decrease the chance of cancer returning, to prevent a new breast cancer, as well as to treat cancer if it has spread. Endocrine therapy is absorbed and circulates throughout the entire body to destroy cancer cells that may be hidden, thereby preventing future cancer.
There are two common types of medication used for this purpose:
- Tamoxifen: This medication was first approved by the FDA in 1977 for use in breast cancer patients. It stops estrogen from getting into cancer cells by blocking the estrogen receptor. It is useful for patients both before and after menopause. It is currently approved for use in women who are at risk for breast cancer, for those who have had ductal carcinoma in situ removed, for those who have had invasive breast cancer removed and for women who are being treated for metastatic breast cancer.
- Aromatase inhibitors: There are three compounds used in the United States. They are anastrazole (Arimidex), letrozole (Femara) and exemestane (Aromasin). They were first approved by the FDA in 2000. They stop production of estrogen in fat tissue and adrenal glands but do not stop production of estrogen in the ovaries. They are used for women in menopause. They are NOT useful for patients who are pre-menopausal.
The two types of anti-estrogen medication have different side effects.
The medical oncologist will recommend which medication to use and the duration of treatment. There are ongoing research studies that are trying to determine the optimum length of time to take these medications.
Some premenopausal patients are candidates for ovary removal or chemical suppression of ovarian function.