January 15, 2025
Breakthrough Breast Cancer Treatment for Inoperable or Metastatic HER2-Low Breast Cancer
Each subtype of breast cancer has specific characteristics that make it unique. When planning the most effective treatment for each patient, oncologists consider various factors, including whether the growth of the cancer is influenced by hormones or an overgrowth of HER2 protein.
What Does it Mean to Have HER2-Low Breast Cancer?
The breast pathology report will indicate if an overgrowth of the human epidermal growth factor receptor (HER2) protein caused by a gene mutation exists. The level of the protein is measured using an immunohistochemical (IHC) score, which can yield one of three results:
HER2-negative: IHC score of 0 or +1
HER2-positive: IHC score of 3 or more
HER2-low: IHC score of 2+
If considered HER2-positive, a targeted therapy drug is used to slow the protein growth. Until recently, HER2-low breast cancers were classified as HER2-negative despite the presence of low levels of the protein. However, this borderline score is observed in approximately half of breast cancer cases. Until recently, patients would not have received HER2 targeted therapy as part of their treatment plans.
How HER2 Status Impacts the Breast Cancer Treatment Plan
Knowing the HER2 status is an important part of planning breast cancer treatment, as different approaches work better depending on the characteristics of the breast cancer cells. In the past, patients with HER2-low breast cancer were treated with therapies designed for HER2-negative cancers instead of receiving HER2-targeted therapies. Fortunately, many of these patients can now take part in receiving the latest FDA-approved targeted therapy drugs tailored for HER2 protein overgrowth.
Patients diagnosed with HER2-positive breast cancer typically undergo surgery first, followed by chemotherapy and a targeted therapy called trastuzumab. Approved in 1998 for treating HER2-positive breast cancer, early-stage and metastatic patients often respond very well because it targets HER2 protein receptors on breast cancer cells, specifically to stop their reproduction.
Additionally, radiation therapy is often used after surgery to kill any cancer cells left behind. Hormone therapy may be added if the cancer is also estrogen and/or progesterone-positive.
Genetic mutations and the development of targeted therapies to counteract them is an important focus of current breast cancer clinical research. Oncologists, including those at Affiliated Oncologists in the Chicago area, are committed to developing new and improved treatment options for patients with genetic mutations including the HER2 gene mutation.
Targeted Therapies: What They Are and How They Work in Treating Breast Cancer
Targeted therapy drugs work by targeting specific molecules, proteins, or genes in cancer cells to stop them from growing and spreading.
Each targeted therapy drug focuses on a specific gene mutation, protein or molecule to destroy cancer cells while sparing surrounding healthy cells. The type of targeted therapy a patient receives depends on the specific characteristics of their cancer. Each targeted therapy is designed with a purpose, including:
Inducing cancer cell death
Blocking signals that promote blood vessel formation
Aiding the immune system in destroying cancer cells
Slowing the overgrowth of proteins that promote cancer cell growth
Delivering substances, such as chemotherapy or radiation, that kill cancer cells
Targeted therapies called anti-HER2 therapies are used for HER2-positive and HER2-low breast cancers. These therapies bind to the HER2 receptor proteins found on breast cancer cells. The drugs slow down or prevent cancer growth by blocking these receptors from receiving growth signals. Anti-HER2 therapies are explicitly intended for HER2-positive or HER2-low breast cancer, not for HER2-negative breast cancer.
New Hope for Metastatic HER2-low Patients
Clinical trial participants diagnosed with HER2-low breast cancer showed a positive response to a new drug called Enhertu. It received FDA approval in 2022.
Enhertu has three key components that work against cancer in different ways:
One component attaches to the HER2 protein, preventing it from receiving growth signals.
Another component disrupts the cell's ability to replicate.
The final component contains a chemotherapy agent, which helps the targeted therapy bind to HER2 receptors on the cancer cells.
Who Is Eligible to Be Treated with Enhertu?
Patients who have HER2-low breast cancer that cannot be removed surgically may be eligible to receive Enhertu if they meet one of the following requirements:
Have received previous chemotherapy treatment for metastatic breast cancer
Were given chemotherapy before or after surgery and had cancer return within 6 months of completing treatment
The oncologists at Affiliated Oncologists will consider your entire health history and past cancer treatments when determining the most suitable breast cancer treatment plan for you.
Taking Enhertu: What to Expect
If your breast cancer specialist has identified you as a good candidate for Enhertu, you can expect to receive the medication through an IV infusion. Enhertu is delivered directly into your bloodstream through a port or an IV into a vein.
While treatment plans may vary, most patients can expect to receive this medication every three weeks.
There are some side effects of Enhertu that you should be aware of, as with most types of cancer treatment. Talk to your oncology team if you receive Enhertu and experience:
Lung issues including a cough, trouble breathing or shortness of breath, shortness of breath or wheezing
Heart issues such as an irregular heartbeat, dizziness or feeling light-headed, loss of consciousness
Sudden weight gain
Swollen ankles or legs
The Latest Breast Cancer Treatments Are Available in the South Chicago Area
Affiliated Oncologists is proud to offer this new, emerging treatment to our breast cancer patients who qualify. If you or someone close to you was recently diagnosed with HER2-low breast cancer, our breast cancer doctors will work closely with you to determine a personalized treatment approach that meets your specific needs. We also provide second opinions to help you feel confident about your diagnosis and recommended treatment plan.
Our cancer centers are in Chicago Ridge, Mokena, Hazel Crest, Orland Park, and Palos Heights, Illinois.
Categories: Breast Cancer