This Know More installation explores HER2-positive breast cancer, from diagnosis through treatment options to future monitoring. Former Komen Scholar Ian Krop, M.D., Ph.D., described the shift in progress for HER2-positive breast cancer in a previous Komen webinar as, “It used to be a diagnosis we really hated to give . . . but now people with HER2-positive disease actually generally do better than people with other types of breast cancer because of new therapies.”
This blog will walk you through understanding the different dimensions of HER2-positive (HER2+) breast cancer to empower you to know what to expect through your own diagnosis or supporting a loved one.
What is HER2-Positive Breast Cancer?
HER2+ breast cancers are defined by a biomarker, a molecule in your body that provides information about your health. In this case, the biomarker is the HER2 protein – short for “human epidermal growth factor receptor 2”. HER2+ breast cancers have this protein in higher-than-normal levels on the surface of breast cancer cells. About 10-20% of newly diagnosed breast cancers are HER2+, and when a tumor overexpresses or has too many HER2 proteins, it encourages the cancer cells to grow and divide more quickly, making the cancer more aggressive. However, thanks to many years of research advancements, HER2+ breast cancers are highly treatable with targeted therapies that block the HER2 protein and slow or prevent its effects. You can see a simplified breakdown of how HER2 works in the video below.
A biopsy of your breast cancer tissue is used to determine your HER2 receptor status, along with hormone receptors, like estrogen receptor (ER) and progesterone receptor (PR) status. All breast cancers are tested for HER2 status. Knowing a tumor’s receptor status is key to helping your care team know what treatments can help to stop or slow cancer growth.
HER2+ cancers can be:
- HER2+ and hormone receptor positive (ER+ or PR+), sometimes called triple positive
- HER2+ and hormone receptor negative (ER-/PR-)
The combination affects whether your treatment might involve both HER2-targeted therapy and hormone therapy or just HER2-targeted therapy alone.
HER2+ cancer can also be metastatic, or stage 4, meaning that the cancer has spread beyond the breast and nearby lymph nodes to other parts of the body. In cases of metastatic HER+ breast cancer, treatment will be lifelong with the continued goal to shrink or slow down tumor growth while maintaining quality of life for as long as possible. Up to 50% of metastatic HER2+ cases can develop brain metastasis, but newer treatments that cross the blood-brain barrier have improved care for people with brain metastasis. For example, HER2-targeting tyrosine kinase inhibitors (tucatinib, neratinib and lapatinib) are known to pass through the blood-brain barrier and may help delay cancer progression.
You may also hear about HER2-low breast cancer. These breast cancers have small amounts of HER2 protein but in levels that fall below the threshold for a HER2+ diagnosis. Recent advances like trastuzumab deruxtecan, the first FDA-approved therapy specifically for HER2-low metastatic breast cancer, have expanded treatment options for this group.
How is HER2+ Breast Cancer Treated?
Treatments for HER2+ breast cancer often include a combination of:
- HER2-Targeted Therapy: Drugs like trastuzumab help block the HER2 receptor, preventing cancer cells from growing.
- Chemotherapy: Often in combination with HER2-targeted therapy, chemotherapy targets and kills rapidly dividing cells.
- Surgery: A lumpectomy or mastectomy may be chosen depending on the size and spread of the tumor, which is often followed by radiation and/or systemic therapy.
- Radiation therapy: Radiation helps reduce the risk of breast cancer returning (recurrence) in the breast or nearby lymph nodes.
- Hormone therapy: If the tumor is hormone receptor-positive (HR+), your doctor might recommend hormone therapies like tamoxifen or aromatase inhibitors.
- Antibody-drug conjugates (ADCs): These drugs, like trastuzumab deruxtecan (Enhertu), deliver chemotherapy directly to HER2+ cancer cells.
Life and Monitoring After Treatment for Early-Stage Breast Cancer
Following active treatment, regular follow-up tests, scans and bloodwork support the monitoring for cancer recurrence and any long-term side effects from treatment.
Some areas to monitor include:
Heart health: HER2 therapies, including trastuzumab, can sometimes affect heart function. In a clinical trial led by Slamon and others, about 2% to 3% of people who received chemotherapy plus trastuzumab developed congestive heart failure, compared to fewer than 1% of those who received chemotherapy alone. While the risk is low, it can be serious, so your care team will likely monitor your heart function regularly during and after treatment. The risk of heart problems may also be higher for people over 60 or those with a history of heart conditions.
Bone health: Bone density can be affected by some treatments, especially hormone therapy and chemotherapy. Periodic bone scans or vitamin supplementation are not uncommon.
Emotional well-being: The fear of recurrence, fatigue and anxiety can be common, and it’s always valid to feel what you experience. Support groups, counseling and Komen’s Patient Care Center are some of the resources that can help provide guidance and support.
Research in Progress
HER2+ breast cancer tends to be more aggressive; however, treatments have improved dramatically in recent decades, and clinical trials continue to show promise. Antibody drug conjugates have revolutionized the treatment of HER2-positive breast cancer, and ongoing studies are determining whether treating with these drugs earlier on improves outcomes. On the other hand, some people with less aggressive tumors respond so well to current treatments that researchers are investigating whether giving less treatment can reduce side effects while maintaining effectiveness. Clinical trials are exploring shorter durations of HER2-targeted drugs or lower-intensity chemotherapy for early-stage patients, which can offer hope for fewer long-term complications. Talk to your doctor about whether a clinical trial could be right for you.
Once considered one of the most aggressive breast cancers, HER2+ breast cancer is now one of the most treatable, thanks to revolutionary targeted therapies and research.
If you’re facing a breast cancer diagnosis and are not sure where to begin, you’ve come to the right place. Our Know More series will continue to help educate you and arm you with the tools you’ll need to feel empowered to advocate for yourself through your experience.
Content covered in the Know More Educational Series may be an emerging area in research or technology. Talk with your doctor about what is right for you.
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Downloadable Resource: Questions to Ask Your Doctor
Learn More:
HER2-Targeted Therapies for Early Breast Cancer PDF
Quick Facts: HER2-Targeted Therapy (2021) PDF
Metastatic HER2+ Targeted Therapies PDF
Understanding HER2-Targeted Therapies Watch
HER2 Basics: What Patients Should Know Watch
Breast Cancer Breakthroughs: HER2+ Research Update Watch
Future Directions in HER2+ Treatment Watch
Do you need help? We’re here for you. The Komen Patient Care Center is your trusted, go-to source for timely, accurate breast health and breast cancer information, services and resources. Our navigators offer free, personalized support to patients, caregivers and family members, including education, emotional support, financial assistance, help accessing care and more. Get connected to a Komen navigator by contacting the Breast Care Helpline at 1-877-465-6636 or email helpline@komen.org to get started. All calls are answered Monday through Thursday, 9 a.m. to 7 p.m. ET and Friday, 9 a.m. to 6 p.m. ET. Se habla español.
