Breast cancer is not a single disease. It’s actually a group of diseases. When diagnosing breast cancer, one of the first steps is identifying what type you have. The breast cancer type provides key information about how the cancer may behave.

When you have a breast biopsy, the tissue is tested for hormone receptors (HR). It’s also tested for something called human epidermal growth factor receptor 2 (HER2). Each can be involved in the development of breast cancer.

In some pathology reports, HER2 is referred to as HER2/neu or ERBB2 (Erb-B2 receptor tyrosine kinase 2). Hormone receptors are identified as estrogen (ER) and progesterone (PR).

The HER2 gene creates HER2 proteins, or receptors. These receptors help control the growth and repair of breast cells. An overexpression of HER2 protein causes out-of-control reproduction of breast cells.

HER2-positive breast cancers tend to be more aggressive than HER2-negative breast cancers. Along with tumor grade and cancer stage, HR and HER2 status help determine your treatment options.

Continue reading to learn more about HER2-positive breast cancer and what you can expect.

At this time, there has been no specific research on survival rates for HER2-positive breast cancer alone. Current studies on breast cancer survival rates apply to all types.

According to the National Cancer Institute (NCI), these are the 5-year relative survival rates for women diagnosed between 2009 and 2015:

  • localized: 98.8 percent
  • regional: 85.5 percent
  • distant (or metastatic): 27.4 percent
  • all stages combined: 89.9 percent

It’s important to remember that these are only overall statistics. Long-term survival statistics are based on people who were diagnosed years ago, but treatment is changing at a rapid pace.

When considering your outlook, your doctor must analyze many factors. Among them are:

  • Stage at diagnosis: The outlook is better when breast cancer hasn’t spread outside the breast or has spread only regionally at the start of treatment. Metastatic breast cancer, which is cancer that has spread to distant sites, is harder to treat.
  • Size and grade of primary tumor: This indicates how aggressive the cancer is.
  • Lymph node involvement: Cancer can spread from the lymph nodes to distant organs and tissues.
  • HR and HER2 status: Targeted therapies can be used for HR-positive and HER2-positive breast cancers.
  • Overall health: Other health issues may complicate treatment.
  • Response to therapy: It’s hard to predict if a particular therapy will be effective or produce intolerable side effects.
  • Age: Younger women and those over the age of 60 tend to have a worse outlook than middle-aged women, with the exception of those with stage 3 breast cancer.

In the United States, it’s estimated that more than 41,000 women will die from breast cancer in 2019.

About 12 percent of women in the United States will develop invasive breast cancer at some point. Anyone, even men, can develop HER2-positive breast cancer. However, it’s more likely to affect younger women. About 25 percent of all breast cancers are HER2-positive.

HER2-positive breast cancer is more aggressive and more likely to recur than HER2-negative breast cancer. Recurrence can happen any time, but it usually takes place within 5 years of treatment.

The good news is that recurrence is less likely today than ever before. This is largely due to the latest targeted treatments. In fact, most people treated for early stage HER2-positive breast cancer don’t relapse.

If your breast cancer is also HR-positive, hormonal therapy may help reduce the risk of recurrence.

HR status and HER2 status can change. If breast cancer recurs, the new tumor must be tested so treatment can be reevaluated.

Your treatment plan will probably include a combination of therapies such as:

Hormone treatments may be an option for people whose cancer is also HR positive.

Surgery

The size, location, and number of tumors help determine the need for breast-conserving surgery or mastectomy, and whether to remove the lymph nodes.

Radiation

Radiation therapy can target any cancer cells that may remain after surgery. It can also be used to shrink tumors.

Chemotherapy

Chemotherapy is a systemic treatment. Powerful drugs can seek out and destroy cancer cells anywhere in the body. HER2-positive breast cancer generally responds well to chemotherapy.

Targeted treatments

Targeted treatments for HER2-positive breast cancer include:

Trastuzumab (Herceptin)

Trastuzumab helps blocks cancer cells from receiving chemical signals that spur growth.

A 2014 study of more than 4,000 women showed that trastuzumab significantly reduced recurrence and improved survival when added to chemotherapy in early stage HER2-positive breast cancer. The chemotherapy regimen consisted of paclitaxel after doxorubicin and cyclophosphamide.

The 10-year survival rate increased from 75.2 percent with chemotherapy alone to 84 percent with the addition of trastuzumab. Rates of survival without recurrence also continued to improve. The 10-year disease-free survival rate increased from 62.2 percent to 73.7 percent.

Ado-trastuzumab emtansine (Kadcyla)

This drug combines trastuzumab with a chemotherapy drug called emtansine. Trastuzumab delivers emtansine directly to the HER2-positive cancer cells. It can be used to shrink tumors and extend survival in women with metastatic breast cancer.

Neratinib (Nerlynx)

Neratinib is a year-long treatment that’s used in the early stages of HER2-positive breast cancer. It’s given to adults who’ve already completed a treatment regimen that includes trastuzumab. The aim of neratinib is to reduce the likelihood of a recurrence.

Targeted therapies usually work from outside the cell to block the chemical signals that promote tumor growth. Neratinib, on the other hand, affects chemical signals from within the cell.

Pertuzumab (Perjeta)

Pertuzumab is a drug that works much like trastuzumab. However, it attaches to a different part of the HER2 protein.

Lapatinib (Tykerb)

Lapatinib blocks proteins that cause uncontrolled cell growth. It can help to delay disease progression when metastatic breast cancer becomes resistant to trastuzumab.

According to estimates, more than 3.1 million women in the United States have a history of breast cancer.

The outlook for HER2-positive breast cancer varies from person to person. Advancements in targeted therapies continue to improve the outlook for both early stage and metastatic disease.

Once treatment for nonmetastatic breast cancer ends, you’ll still need periodic testing for signs of recurrence. Most side effects of treatment will improve over time, but some (such as fertility issues) may be permanent.

Metastatic breast cancer isn’t considered curable. Treatment can continue as long as it’s working. If a particular treatment stops working, you can switch to another.