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. This 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).

HER2 is a gene that creates HER2 proteins, or receptors. These receptors help control 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 helps 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 American Cancer Society, these are the five-year relative survival rates for women with all types of breast cancer:

  • stage 0 or stage 1 (also known as localized or nonmetastatic): nearly 100 percent
  • stage 2: 93 percent
  • stage 3: 72 percent
  • stage 4 (also known as metastatic): 22 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 it 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 is estimated that more than 40,000 women will die from breast cancer in 2017.

Approximately 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. But it’s more likely to affect younger women. HER2-positive represents about 20 percent of all breast cancers.

HER2-positive breast cancer is more aggressive and more likely to recur than HER2-negative breast cancer. Recurrence can happen anytime. But it usually takes place within five 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 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:

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

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.

HER2-positive breast cancer can also be HR-positive. If so, hormone treatments may be an option.

Targeted treatments for HER2-positive breast cancer include:

  • Trastuzumab (Herceptin) helps blocks cancer cells from receiving chemical signals that spur growth. A 2014 study of more than 4,000 women showed that when added to chemotherapy (paclitaxel after doxorubicin and cyclophosphamide) in early stage HER2-positive breast cancer, trastuzumab resulted in a significant reduction in recurrence and improvement in survival. The 10-year survival improved from 75.2 percent with chemotherapy alone to 84 percent with the addition of trastuzumab. Results also demonstrated continued improvement of survival without recurrence. The 10-year disease-free survival rate increased from 62.2 percent to 73.7 percent.
  • Ado-trastuzumab-emtansine (Kadcyla) 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.
  • Pertuzumab (Perjeta) is a drug that works much like trastuzumab. However, it attaches to a different part of the HER2 protein.
  • Lapatinib (Tykerb) blocks proteins that cause uncontrolled cell growth. It can help to delay disease progression when metastatic breast cancer becomes resistant to trastuzumab.

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 may be permanent.

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

According to estimations, 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.