HER2 Status Has Implications for Breast Cancer Treatment and Nursing Care

April 22, 2021

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Breast cancer is classified by several factors, including the presence of human epidermal growth factor receptor 2 (HER2), a type of (https://www.cancer.org/cancer/breast-cancer/understanding-a-breast-cancer-diagnosis/breast-cancer-her2-status.html) growth-promoting (https://doi.org/10.1155/2014/852748) protein found on the surface of cells. All breast cells have HER2 receptors, but some breast cancers have more HER2 receptors than normal, which may promote tumor growth. About 60% of breast cancers have (https://doi.org/10.1200/jco.2014.55.4139) some level (https://doi.org/10.5858/arpa.2012-0617-OA) of HER2 expression, and approximately one in five patients has (https://doi.org/10.2217/cer.12.43) high levels of the HER2 protein, which is considered (https://www.cancer.org/cancer/breast-cancer/understanding-a-breast-cancer-diagnosis/breast-cancer-her2-status.html) HER2-positive.

HER2 Testing and What the Results Mean

HER2 status is one of several factors, including (https://www.cancer.org/cancer/breast-cancer/understanding-a-breast-cancer-diagnosis/breast-cancer-her2-status.html) hormone receptor (HR) status, tumor size, and evidence of metastasis, clinicians use to understand disease prognosis and determine a treatment approach. Patients’ HER2 status is measured by two methods: immunohistochemistry (IHC) and in situ hybridization (ISH). IHC testing measures (https://www.cancer.org/cancer/breast-cancer/understanding-a-breast-cancer-diagnosis/breast-cancer-her2-status.html) the amount of HER2 protein, with results reported as 0, 1+, 2+ or 3+.

Implications for Treatment and Beyond

Breast cancer is typically treated with various combinations of surgery, radiation, chemotherapy, hormone therapy, or targeted therapy. Targeted therapies may be used for specific breast cancer types: HR-positive breast cancers are typically treated (https://doi.org/10.5858/arpa.2012-0617-OA) with endocrine therapies, whereas treatments that target HER2 may be used (https://doi.org/10.18632/oncotarget.7043) for HER2-positive breast cancers.

Targeted agents have unique side effects that oncology nurses must monitor and manage. For example, monoclonal antibodies that target HER2 could affect (https://voice.ons.org/news-and-views/breast-cancer-prevention-screening-diagnosis-treatment-side-effect-and-survivorship) cardiac function, so patients require regular ejection fraction evaluation. If adverse events progress beyond grade 1, doses may need to be adjusted, held, or discontinued, depending on the toxicity’s severity.

The development of targeted therapies has significantly improved survival for patients with HER2-positive breast cancer. Some of the nursing considerations for breast cancer survivorship care include (https://voice.ons.org/news-and-views/nursing-considerations-for-breast-cancer-survivorship-care):

However, HER2-positive metastatic breast cancer remains (https://doi.org/10.18632/oncotarget.7043) an incurable disease. Once patients progress on currently available anti-HER2 regimens, they have few treatment options. Most available therapies for patients with advanced disease have shown limited overall response rates and median progression-free survival benefits of less than six months beyond the second-line setting. Recent advancements in later-line therapy, including monotherapy and combination treatments, that target HER2-expressing metastatic breast cancer may offer meaningful clinical benefit.

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