HER2-Positive Breast Cancer: Treatment and Prognosis

HER2-Positive Breast Cancer at a Glance 

• About 15 to 20 percent of breast cancers are HER2-positive. 
• HER2-positive cancers tend to grow faster than some other breast cancers. 
• Targeted HER2 therapies have dramatically improved outcomes. 
• HER2-positive cancers may also be hormone receptor-positive. 
• Treatment often includes targeted therapy, surgery, chemotherapy and/or radiation. 

A breast cancer diagnosis can bring a flood of new medical terms, and HER2-positive is one many people have never heard before. Knowing a tumor’s HER2 status helps your care team determine which treatments are most likely to work. 

This type of cancer tends to grow faster than other types. However, advances in targeted therapies over the past two decades have dramatically improved outcomes, making this once particularly aggressive cancer much more treatable than it was in the past. 

Here’s what you should know about HER2-positive breast cancer, how it’s diagnosed and the treatment options available today. 

What Does It Mean to Be HER2-Positive? 

HER2 stands for human epidermal growth factor receptor 2, a protein found on the surface of breast cells that normally helps regulate cell growth and repair. 

According to the American Cancer Society, 15 to 20 percent of breast cancer cases are HER2-positive, meaning the cancer cells have higher-than-normal levels of HER2 protein due to changes in the HER2 gene. This excess protein can send signals that encourage cancer cells to grow and divide more rapidly. 

Because of this rapid growth, this type of breast cancer was once considered one of the more aggressive forms of the disease. Today, however, targeted medications designed specifically to block the HER2 protein have significantly improved survival rates and reduced the risk of recurrence. 

What Are the Symptoms of HER2-Positive Breast Cancer? 

Symptoms are the same as those seen with other types of breast cancer and may include: 

• A new breast lump or thickening 
• Changes in breast size or shape 
• Nipple discharge 
• Nipple inversion 
• Skin dimpling 
• Redness or swelling 
• Swollen lymph nodes under the arm 

How Is HER2-Positive Breast Cancer Diagnosed? 

After a breast biopsy confirms breast cancer, the tumor is tested for biomarkers — proteins or other features that help doctors understand the cancer and choose the most effective treatment.

The three biomarkers routinely tested in breast cancer are:

• Estrogen receptor (ER)
• Progesterone receptor (PR)
• HER2

Your care team may also look at Ki-67, a marker that shows how quickly cancer cells are dividing. A higher Ki-67 level generally means the cells are growing and dividing more quickly.

HER2 status is typically determined using one of two tests:

• Immunohistochemistry (IHC): Measures the amount of HER2 protein on the surface of cancer cells.
• Fluorescence in situ hybridization (FISH): Looks for extra copies of the HER2 gene, often when IHC results are unclear.

These results help determine whether the cancer is HER2-positive, HER2-negative or HER2-low and whether HER2-targeted therapies may be part of the treatment plan.

Hormone Receptor-Positive Breast Cancer 

Hormone receptor-positive breast cancers have estrogen receptors (ER), progesterone receptors (PR) or both. 

• Estrogen receptor-positive (ER+) cancers use estrogen to help fuel their growth.
• Progesterone receptor-positive (PR+) cancers use progesterone to help fuel their growth. 

These cancers often respond well to hormone therapy, which blocks or lowers hormone levels to help slow or stop cancer growth. 

Triple-Negative Breast Cancer 

Triple-negative breast cancer (TNBC) lacks estrogen receptors, progesterone receptors and HER2. Because it does not have these treatment targets, therapy often relies on chemotherapy, immunotherapy and other newer treatment approaches. 

HER2-Positive Breast Cancer 

This type of cancer has higher-than-normal levels of the HER2 protein or extra copies of the HER2 gene, which can cause cancer cells to grow more rapidly. Some are also hormone receptor-positive, meaning they may be treated with both HER2-targeted therapies and hormone therapy. 

HER2-Low Breast Cancer 

HER2-low breast cancer has some HER2 protein present, but not enough to be classified as HER2-positive. Some patients with advanced HER2-low breast cancer may benefit from newer targeted treatments. 

HER2-Negative Breast Cancer 

HER2-negative breast cancer does not have enough HER2 to benefit from most targeted therapies. Treatment decisions are based on other characteristics of the tumor, including hormone receptor status. 

Other Types of Breast Cancer 

Breast cancer can also be described by where it begins and whether it has spread. Ductal breast cancer begins in the milk ducts, while lobular breast cancer begins in the milk-producing lobules. 

Doctors may also describe breast cancer as in situ (confined to where it began), invasive (grown into surrounding breast tissue), locoregional (spread to nearby lymph nodes) or metastatic (spread to distant parts of the body). 

Inflammatory breast cancer is a rare, aggressive form that can develop quickly and cause redness, swelling and a dimpled appearance of the breast skin. 

Each type has different characteristics and treatment approaches, making an accurate diagnosis an essential first step. 

Treatment Options for HER2-Positive Breast Cancer 

The biggest breakthrough in treating HER2-positive breast cancer has been the development of HER2-targeted therapies. These medications specifically target the HER2 protein, helping slow or stop cancer growth. 

Treatment often includes a combination of therapies, depending on the stage of the cancer, including: 

• Surgery 
• HER2-targeted therapy 
• Chemotherapy 
• Radiation therapy 
• Hormone therapy (if the cancer is also hormone receptor-positive) 

In some cases, HER2-targeted therapy and chemotherapy may be given before surgery to shrink the tumor. In other cases, treatment is given after surgery to help reduce the risk of the cancer returning. 

New treatments are also being studied. Stony Brook Cancer Center is participating in the FLAMINGO-01 Phase III clinical trial, which is testing a tumor vaccine for certain HER2-positive breast cancer patients with residual disease after preoperative chemotherapy.

Your oncologist will recommend the combination of treatments that’s most appropriate for your specific diagnosis. Following treatment, regular follow-up visits, imaging and other monitoring help detect any signs of recurrence and manage potential side effects. 

What Is the Prognosis for HER2-Positive Breast Cancer? 

HER2-positive breast cancer was once considered one of the more aggressive forms because it can grow and spread quickly. Today, advances in HER2-targeted therapies have significantly improved outcomes and reduced the risk of recurrence. 

A person’s prognosis depends on several factors, including: 

• Stage: Describes the size of the tumor, whether nearby lymph nodes are involved and whether the cancer has spread to distant organs.
• Grade: Describes how the cancer cells look under a microscope and how quickly they are likely to grow.
• Hormone receptor status: Shows whether the cancer has estrogen or progesterone receptors.
• Treatment response: Indicates how well the cancer responds to treatment.

Common Questions 

Is HER2-positive breast cancer hereditary? 

Usually, no. HER2-positive breast cancer is typically caused by changes that occur in the cancer cells and is not inherited. However, some people may have inherited genetic mutations that increase their overall breast cancer risk. 

Is HER2-positive breast cancer curable? 

It depends on factors such as the stage of the cancer, whether it has spread and how well it responds to treatment. When diagnosed early, many people with HER2-positive breast cancer respond very well to treatment. 

Can HER2-positive breast cancer come back after treatment? 

Yes. Like other types of breast cancer, HER2-positive breast cancer can recur. The risk depends on factors such as the stage of the cancer, whether lymph nodes were involved and how the cancer responds to therapy. 

Clinical Trial Opportunity

Stony Brook Cancer Center is participating in the FLAMINGO-01 clinical trial for certain patients with HER2-positive breast cancer. Ask your oncology team whether this clinical trial may be appropriate for you.

Learn more about the FLAMINGO-01 clinical trial or call 631-SB-TRIAL (631-728-7425).

At the Stony Brook Cancer Center’s Carol M. Baldwin Breast Care Center, our specialists are dedicated to providing comprehensive care tailored to each patient’s specific type and stage of breast cancer. This includes in-depth diagnostics and a multidisciplinary approach to treatment, ensuring that each patient receives the most effective strategies for their particular cancer subtype. Learn more or call (631) 638-1000 to make an appointment.