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Breast Cancer Medical Oncology Treatments

Women with breast cancer are likely to receive a few different types of treatment depending on the stage, type and hormone status. Many of the treatments for breast cancer are under the supervision of the medical oncologist. These include:

Chemotherapy for Breast Cancer

Chemotherapy uses drugs to kill cancer cells. The drugs that treat breast cancer are usually given through a vein (intravenous) or as a pill. You’ll probably receive a combination of drugs.

You may receive chemotherapy in an outpatient part of the hospital, at the doctor’s office, or at home. Some women need to stay in the hospital during treatment.

Some anticancer drugs can damage the ovaries. If you have not gone through menopause yet, you may have hot flashes and vaginal dryness. Your menstrual periods may no longer be regular or may stop. You may become infertile (unable to become pregnant). For women over the age of 35, this damage to the ovaries is likely to be permanent.

On the other hand, you may remain able to become pregnant during chemotherapy. Before treatment begins, you should talk with your doctor about birth control because many drugs given during the first trimester are known to cause birth defects.

Hormone Therapy for Breast Cancer

Hormone therapy may also be called anti-hormone treatment. If lab tests show that the tumor in your breast has hormone receptors, then hormone therapy may be an option. Hormone therapy keeps cancer cells from getting or using the natural hormones (estrogen and progesterone) they need to grow.

Hormone therapy options before menopause:

If you have not gone through menopause, the options include:

  • Tamoxifen: This drug can prevent the original breast cancer from returning and also helps prevent the development of new cancers in the other breast. As a treatment for metastatic breast cancer, tamoxifen slows or stops the growth of cancer cells that are in the body. It’s a pill that you take every day for 5 years.

In general, the side effects of tamoxifen are similar to some of the symptoms of menopause. The most common are hot flashes and vaginal discharge. Others are irregular menstrual periods, thinning bones, headaches, fatigue, nausea, vomiting, vaginal dryness or itching, irritation of the skin around the vagina, and skin rash. Serious side effects are rare, but they include blood clots, strokes, uterine cancer, and cataracts. You may want to read the NCI fact sheet Tamoxifen.

  • LH-RH agonist: This type of drug can prevent the ovaries from making estrogen. The estrogen level falls slowly. Examples are leuprolide and goserelin. This type of drug may be given by injection under the skin in the stomach area. Side effects include hot flashes, headaches, weight gain, thinning bones, and bone pain.
  • Surgery to remove your ovaries: Until you go through menopause, your ovaries are your body’s main source of estrogen. When the surgeon removes your ovaries, this source of estrogen is also removed. (A woman who has gone through menopause wouldn’t benefit from this kind of surgery because her ovaries produce much less estrogen.) When the ovaries are removed, menopause occurs right away. The side effects are often more severe than those caused by natural menopause. Your health care team can suggest ways to cope with these side effects.

Hormone therapy options after menopause:

If you have gone through menopause, the options include:

  • Aromatase inhibitor: This type of drug prevents the body from making a form of estrogen (estradiol). Examples are anastrozole, exemestane, and letrozole. Common side effects include hot flashes, nausea, vomiting, and painful bones or joints. Serious side effects include thinning bones and an increase in cholesterol.
  • Tamoxifen: Hormone therapy is given for at least 5 years. Women who have gone through menopause receive tamoxifen for 2 to 5 years. If tamoxifen is given for less than 5 years, then an aromatase inhibitor often is given to complete the 5 years. Some women have hormone therapy for more than 5 years. See above for more information about tamoxifen and its possible side effects.

Breast Cancer Targeted Therapy

Some women with breast cancer may receive drugs called targeted therapy. Targeted therapy for breast cancer is when the oncologist prescribes medicines that “target” specific proteins and genes that are already known to promote breast cancer growth in the body. 

There are many different types of cells that make up the human body. There are blood cells, muscle cells, nerve cells, brain cells, and a long list of other types – each with its own unique job to do. Cancer cells can begin to develop when specific genes within these different cells suddenly begin to change abnormally. Oncologists call these changes “genetic mutations.” 

The job of any gene is to tell the cell when to make their proteins. Without these proteins, the cell will not function properly. If the gene mutates, then the production of the proteins changes, too. 

Sometimes, the proteins themselves even change. For example, a mutated protein might accidentally allow the cells to live longer than normal, or it wrongly instructs the cells to divide and multiply when they shouldn’t. If the body builds up too many extra cells, then those extra cells can begin to form a tumor – perhaps even a cancerous one.

Targeted therapy for breast cancer usually does one of three things:

  1. Turns off the protein’s ability to tell the cell when to divide and multiply.
  2. Turns off the cell’s ability to live longer than normal.
  3. Kills the breast cancer cells.

Targeted therapy uses drugs that block the growth of breast cancer cells. This form of cancer treatment can also target certain tissues surrounding the cancerous tumors or other non-cancerous cells (like blood vessel cells) that are helping the cancer to live and perhaps spread.

Targeted therapy for HER2 positive breast cancer

For tumors that are HER2 positive, targeted HER2 – directed antibody therapy is often administered to block the action of the HER2 growth pathway that stimulates the growth of HER2 positive breast cancer cells.

For example, targeted therapy may block the action of an abnormal protein (such as HER2) that stimulates the growth of breast cancer cells. Trastuzumab (Herceptin®) or lapatinib (TYKERB®) may be given to a woman whose lab tests show that her breast tumor has too much HER2.

Trastuzumab (Herceptin®), pertuzumab (Perjeta), ado-trastuzumab (Kadcyla), and neratinib (Nerlynx) are HER2 targeted therapies that may be recommended to treat HER2 positive breast cancer. Doctors often prescribe these medications along with chemotherapy, radiation, or other treatments. 

Common Targeted Therapies for Breast Cancer

Two of the more common targeted therapies used for breast cancer patients include:

  1. Trastuzumab (Herceptin): This monoclonal antibody is an intravenous medication often used to treat HER2-positive breast cancer. It works by blocking the substances that fuel the growth of breast cancer cells, and it can be delivered in combination with chemotherapies or given alone.

    Common side effects of Herceptin include headache, diarrhea, nausea, fever, chills, insomnia, coughing, and heart irregularities. Several similar versions of the drug are also available, including Herzuma, Kanjinti. Ogivri, Ontruzant, and Trazimera. Another variation called a trastuzumab and hyaluronidase injection (Herceptin Hylecta) is injected under the skin.

  2. Pertuzumab (Perjeta): This monoclonal antibody is also an intravenous medication that is sometimes delivered simultaneously with Trastuzumab and chemotherapies to treat HER2-positive, metastatic breast cancer. Perjeta, like Herceptin, works by blocking growth signals to the breast cancer cells; however, it can also alert the patient’s immune system to attack and destroy the breast cancer cells.

    Possible side effects include diarrhea, hair loss, nausea, fatigue, rash, lower white blood cell counts (neutropenia), and peripheral neuropathy (a numbness or tingling sensation in the hands and feet)

Immunotherapy for Breast Cancer

Immunotherapy for breast cancer involves the use of certain prescription medications to boost the immune system so that it can identify and destroy cancer cells more quickly and easily.  Some types of breast cancer will respond to immunotherapy which uses your own body’s immune system to slow or stop the growth of cancer cells. There is a protein on immune cells called “checkpoints” that can be turned on to attack cancer cells. 

Breast cancer cells can disguise themselves as healthy cells so the checkpoints on the cells don’t work correctly to attack the cancer. By using an immunotherapy drug called a checkpoint inhibitor, the immune system can more effectively play a role in tumor control. While currently only approved to treat metastatic triple-negative breast cancer, clinical trials are exploring additional uses.

While your oncologist wants your cancer treatment medications to kill the potentially deadly cancer cells in your body, they do not want those same medications to accidentally kill the healthy cells at the same time. To achieve this goal, a type of drug called a “PD-L1 inhibitor” that blocks the immune system’s ability to produce certain proteins called “checkpoints.”

Breast cancer cells use these checkpoints as a sort of shield that tricks the immune system into thinking that the sickly cancer cells are actually healthy ones. When the immunotherapy medication blocks the production of these checkpoints, the shield is lifted, and the immune system can clearly see those breast cancer cells. That’s when the body’s natural cancer-fighting agents (called T-cells) restore their normal response and attack the cancer cells.

Common Immunotherapies for Breast Cancer Patients

One of the more common drugs prescribed in immunotherapies is:

  • Atezolizumab (Tecentriq): This drug is a PD-L1 inhibitor; PD-L1 is a protein that is found on certain breast cancer tumors and immune cells. This immunotherapy is an intravenous medication, given by IV, and perhaps the most common immune checkpoint inhibitor.
    Possible side effects of Atezolizumab can include nausea, loss of appetite, coughing, fatigue, constipation, and diarrhea. However, it is critically important to report any additional side effects to your cancer care team should they arise. 

While Atezolizumab is the most common Immunotherapy for breast cancer, there are several alternative options that your oncologist might prescribe.

Other breast cancer treatments include:

Compass Oncology - The US Oncology Network