What You Should Know About the New Treatment for HER2-Low Breast Cancer

The FDA recently announced its approval for Enhertu, a new therapy for HER2-low breast cancer. As the first treatment specifically tailored to this cancer subtype, FDA approval makes this targeted cancer treatment option more widely available to everyone. 

What is HER2-low breast cancer?

HER2 is a protein that causes breast cancer cells to rapidly grow when overexpressed.“HER2-low breast cancer is a classification within the HER2 subtype,” said Erev Tubb, M.D,.F.A.C.P.,  medical oncologist, hematologist and medical director of Inspira’s Leading-Edge Cancer Center at Inspira Medical Center Mullica Hill. “HER2-low tumors have some HER2 proteins on the cell surface but not enough to classify them as HER2-positive.” 

Before defining HER2-low, 80 to 85 percent of new breast cancer cases would have been labeled HER2-negative. However, approximately 60 percent of new HER2-negative patients are now considered HER2-low. Before FDA approval for Enhertu, the only treatment options available for HER2-low patients were hormone therapy and chemotherapy. 

How does Enhertu work?

“Enhertu is an antibody-drug conjugate therapy that is administered through intravenous (IV) infusion,” said Dr. Tubb. “Treatment typically occurs every three weeks unless serious side effects develop.” 

Enhertu works against cancerous tumors through two mechanisms. The first part is an anti-HER2 drug that attaches itself to the HER2 protein and stops it from receiving growth signals. The second part is an inhibitor that interferes with a cancer cell’s ability to replicate.

What are the side effects?

The most common adverse reactions to Enhertu are: 

• Nausea and vomiting
• Fatigue
• Hair loss
• Constipation or diarrhea 
• Decreased appetite 
• Anemia
• Low white blood cell counts
• Cough

Although serious side effects are rare, Enhertu can cause heart problems. It can also lead to interstitial lung disease, which is inflammation and scarring of the lungs. While being treated with Enhertu, your provider will monitor you closely for signs of these risks. 

Is Enhertu right for you?

“Enhertu is approved to treat unresectable (unable to be removed by surgery) or metastatic HER2-positive breast cancer in people previously treated with an anti-HER2 medicine,” said Dr. Tubb. “It’s also approved for unresectable or metastatic HER2-low breast cancer in people who have received chemotherapy.” 

Enhertu is not suitable for all patients, including those who are pregnant or plan on becoming pregnant. Many factors, including your medical history, diagnosis and preexisting conditions, will help your doctor determine an optimal treatment plan for you. 

With a team of experienced physicians, Inspira offers advanced specialized cancer care. Learn more about Inspira’s Cancer Services. 

Inspira Health is a high reliability organization (HRO), which means safety is the top priority for patients and staff. To make an appointment, call 1-800-INSPIRA.