HER2-Low Breast Cancer Treatment Breakthrough for Inoperable or Metastatic Breast Cancer

There are several different subtypes of breast cancer based on what is causing the cancer cells to grow. Hormone-positive breast cancers use estrogen or progesterone to fuel the cancer’s growth. HER2-positive breast cancer is another subtype accounting for about 15-20% of breast cancers. For these patients, the human epidermal growth factor receptor (HER2) protein, which normally controls healthy breast cell production, is being overproduced. This is caused by a mutation in the HER2 gene.

If you received a breast cancer diagnosis, testing was probably done right away to see if the cancer is hormone-positive, HER2-positive, or neither. The results of the test direct the breast cancer specialist’s recommendation for the most ideal treatment plan.

There are some patients who test negative for estrogen or progesterone hormone receptors and HER2 receptors. This is called triple-negative breast cancer.

We have learned in recent years that some patients’ test results don’t show HER2-positive, but they still have a level of HER2 overproduction that is fueling the cancer’s growth. Thankfully there is now a way to treat these patients more effectively than ever before.

Understanding HER2-Low Breast Cancer

When the tests are run to determine if the cancer is fueled by hormones or HER2 expressions, the patient is given an immunohistochemical (IHC) score. The score reflects the amount of HER2 receptors that were detected and puts them in one of three different categories:

• HER2-negative: IHC score of 0 or +1

• HER2-positive: IHC score of 3 or more

• HER2-low: IHC score of 2+

The last category was recently developed to include patients who have a borderline score that does not put them into either of the other two categories. They are neither HER2-positive nor HER2-negative.

Previously, HER2-low breast cancers would be classified as being HER2-negative, even though they still express low levels of the protein. Surprisingly, nearly half of breast cancer cases are considered HER2-low.

How HER2 Status Affects Treatments Used

Breast cancers considered HER2-positive are likely to respond well to a targeted therapy called trastuzumab (Herceptin®). These can be early-stage or metastatic breast cancers.

Additional treatments for breast cancer are likely to be used before and/or after surgery, such as chemotherapy, immunotherapy, and radiation therapy, depending on the breast cancer stage. The targeted therapy uniquely directs itself toward the HER2 receptors to block the reproduction of the cancer cells.

At one time, it wasn’t typical for HER2-low patients to be treated with HER2-targeted therapy drugs for their breast cancer. They would be treated as though they were HER2-negative, but that is no longer the case. As long as specific circumstances are present, they now have the chance to use the latest in targeted therapies for breast cancer approved by the FDA for HER2-low breast cancer.

How Targeted Therapies Work for Treating Breast Cancer

Targeted therapy uses drugs that block the growth of breast cancer cells while leaving healthy cells alone. Less damage to the healthy cells surrounding a tumor makes this a beneficial type of treatment.

The type of breast cancer being treated determines what targeted therapies will be used. Different types of targeted therapy and chemotherapy drugs work differently to attack cancer cells. They may work by:

• Delivering cell-killing substances to cancer cells

• Helping the immune system destroy cancer cells

• Interrupting cancer cell growth signals

• Stopping signals that help form blood vessels

• Causing cancer cell death

• Starving cancer cells of the hormones they need to grow

Targeted therapies for HER-2 positive and HER-2 low breast cancers are known as anti-HER2 therapies. Anti-HER2 therapies attach to the HER2 receptor proteins in breast cancer cells and then block the HER2 receptors from receiving growth signals. This results in slowing or stopping the growth of cancer. Only HER2-positive breast cancer or HER2-low breast cancer can be treated with anti-HER2 therapies.

Enhurtu Offers Hope for HER2-low Patients

A new drug called Enhertu has shown positive results in clinical trials when it comes to treating HER2-low breast cancer. It was given FDA approval on August 5, 2022, for this use.

There are three components of Enhertu that work on cancer in different ways:

• One component attaches to the HER2 protein to stop it from getting growth signals

• Another component interferes with the cell's ability to replicate

• The last component contains a chemotherapy agent that helps the targeted therapy drug bind to the HER2 receptors on the cells

Who is Eligible for Treatment with Enhertu?

Patients whose cancers are metastatic or inoperable (can’t be removed with surgery) are eligible for treatment with Enhertu. You must have also been previously treated with chemotherapy for metastatic breast cancer or given chemotherapy following surgical removal and had the cancer return within six months.

The oncologists at Cancer Care Centers of Brevard will consider your entire health history and previous cancer treatment when determining the best next steps in any breast cancer treatment plan.

What to Expect When Taking Enhertu

If your CCCB breast cancer specialist has determined that you are a good candidate for treatment with Enhertu, you can expect to receive the medication through an IV infusion. Enhertu is delivered directly to your bloodstream through a specialized type of IV called a central line or cancer port.

While treatment plans may vary, most patients can expect to receive this medication every three weeks.

Groundbreaking Cancer Treatments Available in Brevard County

Cancer Care Centers of Brevard is proud to offer this new, emerging treatment to our breast cancer patients who qualify. Request an appointment at one of our convenient Brevard County locations, including Palm Bay, Rockledge, Melbourne, and Merritt Island, FL.

Categories: Breast Cancer