Breast CancerImmunotherapyMetastatic Breast Cancer

Immunotherapy for the Management of Triple-Negative Metastatic Breast Cancer

Immunotherapy is a welcome new option in the treatment of triple-negative disease. Here’s how it works.
October 2020 Part 4 of 4 – Breast Cancer Special Issue Series
Lillie D. Shockney, RN, BS, MAS, HON-ONN-CG
Co-Founder, Academy of Oncology Nurse & Patient Navigators® (AONN+)
Editor-in-Chief, Journal of Oncology Navigation & Survivorship®
University Distinguished Service Professor of Breast Cancer
Professor of Surgery, Johns Hopkins University School of Medicine
Co-Developer, Work Stride: Managing Cancer at Work
Johns Hopkins Healthcare Solutions
Breast cancer survivor

You have been reading about various forms of management of your disease. Now let us discuss one of the newest forms of systemic treatment—immunotherapy. Sometimes immunotherapy is called biologic therapy, or biotherapy, because it uses the body’s own defense system to fight the breast cancer. Researchers who specialize in breast cancer as well as other types of cancer (melanoma, bladder cancer, and lung cancer, for example) have been hard at work to determine if there are medicines that can help the immune system (your own immune system!) do a better job of recognizing a breast cancer cell and thereby also the ability to destroy it. It has only been in the past few years that immunotherapy drugs have begun to show promise for triple-negative metastatic breast cancer. Before, however, there were other types of breast cancers that could be treated with specific immunotherapy drugs because of specific genetic features. Patients usually have to be enrolled in a clinical trial to get access to immunotherapy.

Let us talk about how this new and exciting classification of drug therapy works. Your immune system is very complicated, probably far more than scientists ever imagined. It is made up of a complex group of organs and cells that carry out their work by defending the body against bacteria, viruses, and other infectious organisms. Most of the time, your body’s immune system recognizes when cells are harmful to the body and attacks these cells to prevent you from getting sick. When your immune system is very taxed, it can be difficult for it to function well. Think about the chaotic time between Thanksgiving and New Year’s Day when you have too much to do and not enough time to do it. After the holidays are over, you suddenly get a cold or catch the flu. This is because your immune system has been working hard and under stress during that time, and it was not able to prevent bacteria or a virus from entering your body and staying there for its normal duration of a week to 10 days. And, unfortunately, adding to the challenge of your body being able to fight off cancer cells, cancer cells look so much like healthy cells that your immune system cannot distinguish them from your healthy cells. This is why your immune system is not able to heal your body of cancer on its own like it can a cold or flu. Immunotherapy can also change the breast cancer cells themselves to make them seem more foreign or abnormal, which helps the immune cells recognize them and attack them.

By taking special immunotherapy drugs, the immune system becomes stronger and focuses on the specific parts of the breast cancer cells that are different from normal healthy cells. Once the immune system can differentiate between the two, the odds are better that it can attack the cancer cells and destroy them. Many immunotherapies target certain gene mutations or even have the power to alter the cancer cell’s own DNA. This DNA is not present in the healthy cells, thus leaving those cells unaffected. It is not surprising then that breast cancer cells with the most mutations within them have the best chance of responding well to immunotherapy.

Immunotherapy is administered intravenously every few weeks; it may take from a few minutes to several hours to receive it. And although the mission is for the immunotherapy to help attack the cancer cells, sometimes it attacks healthy cells as well. When that type of side effect, or adverse effect, happens, it can result in serious autoimmune diseases that affect the lungs, kidneys, reproductive system, colon, skin, pituitary and adrenal glands, as well as the thyroid. Patients are closely monitored for these types of disorders while receiving immunotherapy. If you already have an autoimmune disorder, then it may not be in your best interest to receive immunotherapy. Such drug therapy can also lower your white blood cell count, which increases your risk of getting an infection. Your treatment team will be monitoring your blood counts very closely and reminding you to stay away from people who have a cold or the flu or other types of infections because you are at higher risk of catching them while on this therapy. It is pretty common that the main side effects for you will be aches, low-grade fever, and fatigue.

The immunotherapy drug that has demonstrated it works on triple-negative metastatic breast cancer is called a PD-L1 inhibitor. A PD-L1 inhibitor is also known as a checkpoint inhibitor. Its name is atezolizumab (Tecentriq). It actually targets PD-L1, which is a protein that is located on some cancer cells and immune cells. It works by blocking this protein, which helps to boost your immune system to attack the breast cancer cells. In doing so, it can shrink some tumors or slow down their ability to grow bigger. It is commonly given with another drug called Abraxane (albumin-bound paclitaxel) when tests show that your breast cancer cells have the PD-L1 protein.

This is the first immunotherapy to be tested in clinical trials in women like yourself who have triple-negative metastatic breast cancer. Positive study results were seen very early on, even before the usual length of time such clinical trials normally take to complete and analyze the results, and the FDA granted accelerated approval of this specific immunotherapy drug for patients like yourself.

The approval and now use of a new treatment like this are very exciting for women with your clinical situation because, as you likely have learned, patients with triple-negative breast cancers have much fewer drug therapy options than someone who has positive prognostic factors of estrogen, progesterone, and/or HER2 receptors. Ask your medical oncologist if your breast cancer cells have been tested for the presence of the checkpoint inhibitor PD-L1 to determine if this targeted treatment is right for you.

Do not assume this will be the only immunotherapy drug developed for triple-negative metastatic breast cancer either. There are ongoing clinical trials and laboratory research examining the possibility of other potential targeted drugs that may also provide benefit in slowing down or stopping tumor cells from progressing.

Also anticipate to hear about immunotherapy being used in patients with early-stage triple-negative breast cancer. An immunotherapy drug called pembrolizumab (Keytruda), which is also a checkpoint inhibitor, is being given before surgery with chemotherapy (known as neoadjuvant therapy) and is demonstrating shrinkage of the tumor in the breast. In some cases, the shrinkage is so significant that at the time of surgery, the pathologist finds there are no living breast cancer cells within the breast; this is known as a complete pathological response.

Immunotherapy is exciting and has become a focus of extensive research. Today, women with triple-negative breast cancer can benefit from how it uses their own immune system to attack the cancer cells wherever they may be in the body.

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