Immunotherapy for Breast Cancer

Immunotherapy is a type of cancer treatment that uses the body’s immune system to fight cancer cells. The immune system comprises white blood cells and organs and tissues of the lymphatic system to fight diseases and infections.

The immune system can usually detect abnormal cells and destroy them, which can prevent or curb the growth of many cancers. Unfortunately, cancer cells have ways to avoid destruction, including:

• Changing genetically to avoid or reduce detection by the immune system.
• Having proteins on their surface that deactivate immune cells.
• Manipulate the other components of the tumor microenvironment around them, which can affect the immune response.

Immunotherapy aims to target such mechanisms or boost the immune system’s ability to fight cancer.

There are several approaches to immunotherapy for breast cancer:

• Monoclonal antibodies (also called therapeutic antibodies)

Monoclonal antibodies are immune system proteins created in a laboratory designed to bind to specific targets on cancer cells. These make the cancer cells more visible to the immune system and increase the chances of destruction of the cancer cells by the immune system. Trastuzumab is one such drug that has been approved and used for metastatic HER2+ breast cancer in combination with chemotherapy and has become the standard therapy for patients with HER2+ early and late-stage breast cancer.

• Antibody-drug conjugate

Antibiotic-drug conjugate is a more novel approach that uses a monoclonal antibody, a potent chemotherapeutic, and a linker connecting the two. Such an approach has been shown to minimize drug toxicity and increase antitumor immunity (immunity to tumors).

• Immune checkpoint-inhibitors

Immune checkpoints are proteins on immune cells that must be turned on (or off) to trigger an immune response. It is the immune system’s way to regulate and manage the immune response. Breast cancer cells sometimes use these checkpoints to avoid detection and response by the immune system. Immune checkpoint-inhibitors target these proteins, increasing the immune response against breast cancer cells.

Despite the increase in rates of benefit and survival in tumor patients, some, unfortunately, do not respond to initial immunotherapy, and some develop a resistance to treatment. This resistance may happen through:

• Intrinsic mechanisms

Genetic changes in tumor cells, tumor signaling pathways, and antitumor response pathways may create resistance to immunotherapy.

• Extrinsic mechanisms

Extrinsic mechanisms may involve other normal cells around the tumor, which can affect the immune response.

Several approaches have to be considered to overcome resistance to immunotherapy. For example, a therapeutic combination of several antibodies may contribute to improved patient survival. More research has to be done in this field for it to be more widely applicable, but the potential is enormous.

• Fatigue
• Cough
• Nausea
• Skin rash
• Poor appetite
• Constipation
• Diarrhea
• Infusion reaction
• Autoimmune reactions

It is of utmost importance to ensure that your healthcare team is aware of any newly experienced side effects from the drug. This is due to the drug's functions to potentially activate the immune system to attack other body parts, which can result in serious and life-threatening problems. Therefore, timely communication of such symptoms to your healthcare team can help avoid any potential risks and ensure the best possible outcomes for your health.