How Immunotherapy Is Used to Treat Triple-Negative Breast Cancer

Traditionally, only chemo has worked against this breast cancer subtype.

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Triple-negative breast cancer gets its name because it’s lacking all three receptors typically found on breast cancer cells—namely estrogen, progesterone, and HER2 receptors. In other types of breast cancer, these receptors help fuel the growth of the breast cancer.

Knowing the receptor status for an individual’s breast cancer influences which treatment will be most effective. Those with estrogen or progesterone receptors benefit from hormone therapy, and those with HER2 receptors benefit from targeted therapy against the HER2 protein.

The result: Women with triple-negative breast cancer have not been able to benefit from these newer, more effective treatments against breast cancer. “Traditionally, chemotherapy is the mainstay of treatment for triple-negative breast cancer,” says Amy Tiersten, MD, hematologist and oncologist at Dubin Breast Center, Mount Sinai Hospital in New York City. Learn more about treating triple-negative breast cancer here.

Although chemotherapy tends to be more effective against triple-negative breast cancer than other types of cancer, it can be a harsh treatment that causes a number of side effects, like hair loss, mouth sores, and nausea. That’s because it attacks all rapidly dividing cells indiscriminately, so it affects many normal cells in addition to cancer cells.

A Breakthrough in Triple-Negative Breast Cancer Treatment

“There was just a very exciting study that came out in the fall leading to the FDA approval of one of the immunotherapy drugs, showing for the first time effectiveness for immunotherapy in combination with chemotherapy for triple-negative breast cancer,” says Dr. Tiersten.

Immunotherapy is a class of drugs that stimulate the body’s own immune system to differentiate cancer cells from normal, healthy cells, allowing it to initiate an immune response to kill the cancer cells. There are different types of immunotherapy, but the one that has been approved for triple-negative breast cancer is a checkpoint inhibitor.

This particular checkpoint inhibitor for triple-negative breast cancer works by blocking a protein on the cancer cell known as PD-L1. This PD-L1 protein is what hides the cancer from the immune system. With this immunotherapy drug, that protein is blocked and the immune system is able to recognize the cancer cell, and then shrink or eliminate the tumor.

A major benefit to immunotherapy is that because it’s going directly after cancer cells, it tends to cause fewer and milder side effects than chemotherapy. (Learn more about the difference between immunotherapy and chemotherapy.)

The recent study—which combined checkpoint inhibitors with chemotherapy—was “the first trial that showed any benefit for immunotherapy” for breast cancer, and particularly for triple-negative breast cancer, says Dr. Tiersten.

These immunotherapy drugs “really have the potential to improve the outcome for these women in terms of reducing risk of recurrence [in the early stages], as well as life-prolonging therapies for patients with more advanced disease,” says Dr. Tiersten.