HER2-positive breast cancer is a subtype of breast cancer that contains human epidermal growth factor receptor 2 (HER2), which is a protein that increases the growth of cancer cells. One out of five breast cancers contain the HER2 protein. Eighteen-to-twenty percent of invasive breast cancers are HER2-positive, which are more aggressive than other breast cancers, more likely to spread and relapse, and have resulted in a decreased survival rate in the past. While previously considered to be the most aggressive type of breast cancer, HER-2 positive breast cancer can now be treated with new biologic targeted therapies that have significantly improved outcomes. HER2-positive breast cancer is categorized in stages that take into account the diameter of the tumor, whether the cancer has spread to axillary (underarm) lymph nodes, and whether the cancer has spread to other organs, such as the liver, lung, brain and bone. Staging allows for treatment plans that target each patient’s individual breast cancer disease. Early breast cancers are staged based on the following criteria: Stage 0 – Ductal cancer in situ (DCIS), or a noninvasive breast cancer that is limited to the ducts. Stage I (A/B) – Cancer has spread from ducts to the surrounding fatty breast tissue. Tumor is smaller than 2 centimeters and has not spread to lymph nodes. Stage II (IIA/B) – Cancer has spread from ducts to the surrounding fatty breast tissue and may have spread to near lymph nodes. Tumor is between 2-to-5 centimeters wide. Advanced breast cancers are staged based on the following criteria: Stage III (IIIA/B) – The tumor is larger than 5 centimeters, cancer may or may not have spread to lymph nodes, or the tumor is smaller, and cancer has spread to lymph nodes. Stage IV – Metastatic Breast Cancer. Cancer has spread to lymph nodes and other parts of the body, with other organs affected, such as liver, lungs, brain, or bones.

HER2-positive breast cancer may also be referred to as HER2+breast cancer, HER breast cancer, or human epidermal growth factor receptor 2 positive breast cancer.

The causes of HER2-positive breast cancer are currently unknown, as researchers do not know what makes this breast cancer contain the human epidermal growth factor receptor 2 (HER2) protein.

Symptoms for HER2-positive breast cancer are the same as other breast cancers, with the exception that this breast cancer grows and spreads more rapidly. The most common initial symptom is the discovery of a painless, hard mass with uneven edges, although some breast cancer lumps can also be tender, or even painful, soft, and round. Additional symptoms of breast cancer may include breast swelling, breast or nipple pain, nipple discharge, nipple or breast skin that is reddened, dry, flaking, or thickened, nipple discharge, nipple retraction, orange peel skin (dimpling), and swollen lymph nodes (usually under the arm or around the collarbone).

While previously considered to be the more aggressive type of breast cancer, today HER2-positive breast cancer can be treated with biologic targeted therapies, also known as monoclonal antibodies, such as trastuzumab emtansine (Kadcyla), that target the human epidermal growth factor receptor 2 (HER2) protein, that are highly effective, allow for a good prognosis, and have increased survival for this cancer by more than 30%. However, some women with HER2-positive breast cancer do not respond to the targeted treatments and/or develop resistance to these medications, which has led to the development of new or modified drug combinations. Other medications include pertuzumab (Perjeta), docetaxel (Taxotere), lapatinib ditosylate (Tykerb), neratinib maleate (Nerylynx), and, most recently, fam-trastuzumab (Enhertu). HER2-positive breast cancer can also be treated with standard chemotherapy. Treatment for HER2-positive breast cancer usually includes a combination of biologic targeted therapies and chemotherapy. Trastuzumab, a biologic targeted therapy, is a monoclonal antibody that works against the HER 2 protein, preventing the growth and spread of cancer cells. Pertuzumab, a biologic targeted therapy, is a monoclonal antibody that works by blocking the HER2 protein from growing and spreading cancer cells. Pertuzumab can be used in combination with trastuzumab and the chemotherapy drug, docetaxel (Taxotere), in women with HER2-positive metastatic breast cancer and as an adjuvant (added after initial treatment) therapy for early breast cancer that has a high risk of recurrence. Ado-trastuzumab emtansine is a monoclonal antibody that is combined with the chemotherapy drug, emtansine. Lapatinib is a kinase inhibitor that is combined with chemotherapy or hormone therapy. Neratinib is a kinase inhibitor that works by stopping cancer cells ability to grow. Fam-trastuzumab was recently approved (2019) by the U.S. Food and Drug Administration (FDA) as a new targeted therapy for unresectable or metastatic HER2-postive breast cancer that continues to metastasize (spread) after treatment with two or more targeted treatments.

There are a variety of support groups for individuals with HER2-positive breast cancer: Breast Cancer.org - https://www.breastcancer.org Cancer Care - https://www.cancercare.org/ Living Beyond Breast Cancer - https://www.lbbc.org/learn/types-breast-cancer/her2-positive-breast-cancer

While HER2-positive breast cancers may grow and spread more quickly, as well as to reoccur after treatment, new biologic targeted therapies have led to a significant improvement, are highly effective, allow for a good prognosis, and have increased survival for this breast cancer by more than 30%.

Complications of HER2-positive breast cancer are related to the cancer itself and/or the side effects of treatment. Advanced breast cancer-related complications include pain and cancer spread (metastasis) to organs such as the liver, lung, brain, and bones. Breast cancer treatment-related complications can include breast swelling and tenderness, scar tissue, wound infection, or bleeding, and swelling of the arm (lymphedema) due to removal of the lymph nodes. Chemotherapy treatment-related complications can include hair loss, fatigue, menopausal symptoms, skin and nail changes, nausea and vomiting, nerve pain, and can possibly affect heart health.

Any changes in the breast, breast skin, or nipple, the appearance of a mass or lump in the breast, pain in the breast, swollen axillary (underarm) lymph nodes, or swollen lymph nodes above or below the collarbone (clavicle) should be evaluated by a medical professional.

Regular screening for breast cancer (mammograms) is recommended. Performing regular breast self-exams and noticing any changes, while being aware of the signs and symptoms of breast cancer, is important for early detection of breast cancer. Patients with invasive breast cancer should be tested for the HER2 protein because its presence will guide treatment decisions. Any recurrent breast cancer or metastatic breast cancer should also be retested for the HER2 protein as well as for hormone receptor status. Early detection of breast cancer can provide a better chance for successful treatment.