- Immunotherapy for breast cancer works by stimulating a person’s immune system to destroy cancer cells.
- Triple-negative breast cancer (TNBC) has a higher recurrence rate than other types of breast cancer.
- Many researchers are interested in TNBC-targeted immunotherapy drugs.
- Most immunotherapy drugs are only available in clinical trials because there can be some severe side effects.
- With immunotherapy, 15-20% of patients achieve durable results.
Immunotherapy for breast cancer gives much-needed hope to patients with Triple-negative breast cancer (TNBC). Immunotherapy drugs trigger your immune system to see and destroy cancer cells in your breast tissue.
Immunotherapy is used, often in conjunction with other therapies like chemotherapy or surgery, to treat some types of breast cancer—specifically, triple-negative breast cancer (TNBC).
About 10-20% of breast cancer patients are diagnosed with triple-negative breast cancer annually. If you are diagnosed with triple-negative breast cancer, you have tested negative for estrogen receptors, progesterone receptors, and HER2-positive breast cancer.
- Estrogen receptors — activated by the hormone estrogen — are a group of proteins found inside cells.
- The progesterone receptor is a protein found inside cells. It is activated by the steroid hormone progesterone.
- HER2-positive breast cancer is a breast cancer that tests positive for a protein called human epidermal growth factor receptor 2 (HER2). This protein promotes the growth of cancer cells. In about one of every five breast cancers, the cancer cells have extra copies of the gene that makes the HER2 protein.
Treatment options for triple-negative breast cancer are limited. That’s because triple-negative breast cancer doesn’t respond to hormone therapy medicines or medicines that target HER2 protein receptors.
Chemotherapy is usually the first-line treatment option. Although TNBC usually responds initially to chemotherapy, it tends to recur more than with other types of breast cancers. This is why immunotherapy for breast cancer stands out as a treatment option.
What is immunotherapy for breast cancer?
Immunotherapy drugs use the power of your body’s immune system to attack cancer cells.
Immunotherapy uses organic or chemical substances to boost the immune system. These can:
- Shut down or inhibit cancer cell growth
- Stop cancer cells from metastasizing (spreading to other parts of your body)
Before we move on, let’s review how the immune system works. For your immune system to respond to a foreign invader, it needs to tell the difference between what is part of you (self) or not part of you (nonself or foreign) and possibly harmful. Cancer cells are harmful, or nonself. Proteins on and inside your cells called antigens help your immune system differentiate between the types of cells.
Your immune system and breast cancer.
You may be curious as to why your immune system doesn’t attack breast cancer cells without the help of immunotherapy drugs.
There are two main reasons for this:
- A breast cancer cell starts as a normal, healthy cell. These cells don’t announce to your immune system that they are nonself like other foreign substances do. That makes it more difficult for your immune system to recognize them and act.
However, as healthy cells become cancerous, they start to produce proteins that your immune system will recognize as foreign antigens. Sometimes, this process is more effective than others, and your immune system can stop cancer cells’ production before cancer can grow more or spread.
- As cancer grows, the nonself cells gain the ability to avoid the immune system. Breast cancer develops over some time. As healthy cells slowly evolve into cancer cells, the genetic information they carry also changes. Some of these genetic mutations allow the malignant tumor cells to hide from the immune system.
Cancer cells also tend to grow and multiple at a faster rate than normal cells. Because of this, the immune system can get overwhelmed and breast cancer can start to grow with abandon.
Two types of immunotherapy medicines.
Researchers who study breast oncology try to figure out how to get the immune system to respond to breast cancer with two kinds of immunotherapies:
- Active immunotherapies prompt your immune system to respond to the cancer. Cells from a tumor are studied to find the cancer’s antigens. Then, an immunotherapy treatment is developed, which causes the immune system to target those antigens. Cancer vaccines and adoptive cell therapy are two examples of active immunotherapies.
- Passive immunotherapies deliver synthetic immune system components to help your body fight cancer. Immune checkpoint inhibitors and cytokines are two kinds of passive immunotherapies.
Because immunotherapy medicines help your immune system combat or eliminate cancer, the process can take a long time.
Many experts think that combining immunotherapies — for example, using a vaccine in combination with a checkpoint inhibitor — may help jump-start a robust immune response to cancer.
Likewise, scientists are looking at how immunotherapies can work in combination with other cancer treatments, such as targeted therapies.
What are targeted immune therapies?
Targeted therapies go after specific aspects of cancer cells, including breast cancer cells. For example, the therapy might target a protein that lets cancer cells grow a great deal.
There are also targeted therapies that act like the organic antibodies produced by your immune system. These help the immune system recognize cancer.
Oncology researchers have created antibodies that specifically target antigens, like the ones specific to malignant tumor cells. These are called monoclonal antibodies. Some of these can spot target proteins on the surface of tumor cells and then bind to them.
When the monoclonal antibody connects to the target protein, it inhibits the target protein’s function and gets rid of the cancer cell.
Two monoclonal antibodies that work like this and are FDA-approved to treat breast cancer are:
- Enhertu (chemical name: fam-trastuzumab-deruxtecan-nxki),
- Herceptin (chemical name: trastuzumab); many other versions of this brand name are available
Several immunotherapy medicines are approved by the U.S. Food and Drug Administration (FDA) to treat breast cancer.
What are immune checkpoint inhibitors?
Immune checkpoints are proteins that assist your immune system in recognizing healthy cells.
Breast cancer cells sometimes use these immune checkpoint proteins as a protective shield to avoid being identified and attacked by the immune system.
Immune system cells called T cells circulate throughout your body to look for signs of disease or infection and to identify cells.
If the surface proteins show that the cell is healthy, the T cell ignores it. If the surface proteins show the tumor cell is malignant, the T cell begins to attack.
Once T cells set upon the malignant cell, your immune system starts to generate more proteins to prevent more damage to normal cells and tissues in the body. These specialized proteins are immune checkpoints.
Immune checkpoint inhibitors go after these immune checkpoint proteins to help the immune system see and attack malignant tumor cells.
Immune checkpoint inhibitors free up the immune system by blocking checkpoint inhibitor proteins on cancer cells or the T cells that respond to them.
There are two types of immune checkpoint inhibitors:
- PD-1, a checkpoint protein found on T cells
- PD-L1, a checkpoint protein found in many healthy cells
When PD-1 binds to PD-L1, it prevents T cells from eliminating the cell. However, some breast cancer cells have many PD-L1 on their surface, preventing the T cells from eradicating cancer cells.
An immune checkpoint inhibitor drug that stops PD-1 from binding to PD-L1 allows T cells to attack the cancer cells.
Some such immune checkpoint inhibitors are:
- Keytruda (chemical name: pembrolizumab) is used in combination with chemotherapy
- Tecentriq (chemical name: atezolizumab) is used in conjunction with Abraxane (chemical name: albumin-bound or nab-paclitaxel).
Both Tecentriq (atezolizumab) and Keytruda (pembrolizumab) are PD-L1 inhibitors approved by the FDA to treat non-surgically removable locally advanced triple-negative breast cancer or metastatic triple-negative breast cancer, or PD-L1-positive breast cancer.
Many other immunotherapy drugs are approved to treat different kinds of cancer, such as lung cancer and leukemia.
Clinical trials are looking at these as well as other PD-1/PD-L1 inhibitors to treat breast cancer.
What are cancer vaccines?
You’re likely familiar with traditional vaccines for things like measles, mumps, polio, and rubella. These are intended to prevent disease.
A lot of the research on vaccines for cancer is centered around cancer treatment rather than prevention. Cancer vaccine treatment doesn’t start until after you’ve been diagnosed. Treatment vaccines prompt the immune system to attack cancer cells.
Since it can take cancer vaccines months to produce a response, they are thought to be more useful as a treatment for preventing cancer recurrence after other therapies, such as surgery, are completed.
Cancer treatments given after surgery are referred to as adjuvant treatments.
As of this article’s publication date, there are several clinical trials for adjuvant breast cancer treatment vaccines, but the FDA has approved no breast cancer vaccines.
What is adoptive T cell therapy?
Adoptive T cell therapy attempts to boost your T cells’ natural ability to identify and eliminate cancer cells.
Breast cancer research has discovered many types of adoptive cell therapy based on how the T cells are treated in the lab:
- Chimeric antigen receptor (CAR) T-cell treatment genetically alters T cells to have chimeric antigen receptors (CARs) on their surfaces.
- Tumor-infiltrating lymphocyte (TIL) and interleukin-2 (IL-2) T cell therapy will remove TILs. TILs are a type of T cell that is found in cancer tumors.
The FDA has not approved adoptive cell therapies to treat breast cancer or any other cancer. This therapy is only available in clinical trials.
What are cytokines?
Cytokines are regarded as non-specific immunotherapy drugs because they don’t respond to a particular target on most breast tumors. Instead, they support the immune system more broadly.
Still, this general boost can lead to a better immune system response to cancer. In many cases, cytokines are given in conjunction with another cancer treatment, like chemotherapy or radiation.
As of this writing, no cytokines are approved by the FDA to treat breast cancer. There are, however, clinical trials.
What are the side effects of immunotherapy drugs for breast cancer?
The most significant side effect stemming from immune checkpoint inhibitor medicines is that they may allow the immune system to go after healthy cells and organs aggressively.
Because the medicines take the brakes off the immune system, T cells may start attacking healthy cells.
Some severe side effects include problems with the lungs, liver, intestines, pancreas, and kidneys.
Is breast cancer immunotherapy right for me?
Immunotherapy medicines are relatively new. They have not been studied as thoroughly as surgery, chemotherapy, radiation therapy, and hormonal therapy.
Given the severe side effects that could occur, many breast cancer immunotherapy drugs are still in clinical trials. They are used for those with advanced triple-negative breast cancer or metastatic triple-negative breast cancer.
It’s difficult to say who will benefit from available immunotherapies or those currently under investigation, such as vaccines.
Much of the breast cancer research looking at immunotherapies focuses on metastatic disease, especially in advanced or metastatic triple-negative breast cancer.
Suppose you have advanced triple-negative breast cancer or metastatic triple-negative breast cancer. In that case, you might consider asking your oncology team about clinical trials around immunotherapy. Numerous clinical studies are being conducted at cancer centers in the United States.
This is a promising time in metastatic breast cancer research. There are dozens of treatments for metastatic breast cancer currently under study, and treatment is improving.
Findings from clinical trials will determine whether these new treatments will become a part of standard care for metastatic breast cancer.
Immunotherapy for breast cancer is developing quickly as new research shows improved outcomes in certain kinds of breast cancer such as TNBC.
Breast cancer immunotherapy: Offering new hope for breast cancer patients.
Traditional breast cancer treatments have included surgery, chemotherapy, radiation and hormone therapy.
Immunotherapy is a class of treatments that may be able to use the power of your immune system to help stop cancer cells.
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