Do you know what your breast cancer diagnosis really means? Even more, do you know how your specific type of breast cancer is going to affect you? Read on to get answers to these questions and others.

When you have a biopsy for a breast tumor, the pathology report tells you a lot more than whether it’s cancerous or not. It provides crucial information about the makeup of your tumor.

This is important because some types of breast cancer are more aggressive than others, meaning they grow and spread faster. Targeted treatments are available for some types, but not for all.

Each type of breast cancer requires its own approach to treatment. The information in your pathology report will help guide your treatment goals and options.

Two important items on the report will be your HR status and your HER2 status.

Continue reading to learn more about how HR and HER2 status in breast cancer affects your treatment and your outlook.

HR is short for hormone receptor. Breast tumors are tested for both estrogen receptors (ER) and progesterone receptors (PR). Each status appears separately on your pathology report.

Approximately 80 percent of breast cancers test positive for ER. About 65 percent of those are also positive for PR.

You can test positive for ER, PR, or both. Either way, it means that hormones fuel your breast cancer. It also means that your treatment can include medications that affect hormones.

It’s also possible to test negative for both hormone receptors. If that’s the case, hormones do not fuel your breast cancer, so hormone therapy wouldn’t be effective.

HER2 is short for human epidermal growth factor receptor 2. In a pathology report, HER2 is sometimes called ERBB2, which stands for Erb-B2 receptor tyrosine kinase 2.

HER2 is a gene that produces HER2 proteins, or receptors.

When the HER2 gene isn’t functioning properly, it reproduces too many copies, which leads to overexpression of the HER2 protein. This causes uncontrolled breast cell division and the formation of tumors. This is known as HER2-positive breast cancer.

HER2-positive breast cancer tends to be more aggressive than HER2-negative breast cancer. However, current therapies targeting the HER2-receptor are so effective that many doctors find it easier to treat.

Your treatment plan will be based on both your HR status and your HER2 status.

Hormonal therapy is usually recommended as the first-line treatment for HER2-negative advanced breast cancer that’s HR-positive.

Your oncology team will make recommendations based on several other factors, including how far the cancer has spread.

HR-positive breast cancer treatments

  • selective estrogen-receptor response modulators (SERMs)
  • aromatase inhibitors
  • estrogen-receptor downregulators (ERDs), some of which are used to treat advanced HR-positive breast cancer
  • luteinizing hormone-releasing hormone agents (LHRHs)
  • removal of the ovaries (oophorectomy)

Some of these drugs lower hormone levels. Others block their effect. The drugs are also used to help prevent cancer from recurring.

About 74 percent of all breast cancers are both HR-positive and HER2-negative.

Breast cancer that starts in the luminal cells that line the mammary ducts is called luminal A breast cancer. Luminal A tumors are usually ER-positive and HER2-negative.

Advanced HR-positive/HER2-negative breast cancer treatments

  • Palbociclib (Ibrance), ribociclib (Kisqali), or abemaciclib (Verzenio) is used in combination with aromatase inhibitors.
  • Everolimus (Afinitor) is used in combination with an aromatase inhibitor called exemestane (Aromasin). It’s intended for those whose cancer progressed while using letrozole (Femara) or anastrozole (Arimidex), both aromatase inhibitors.
  • Alpelisib (Piqray) is used to block a form of the PI3K protein in cancer cells.
  • Fulvestrant (Faslodex) targets a receiver called the estrogen receptor to inhibit cancer cell growth.
  • Tamoxifen is a selective estrogen-receptor response modulator (SERM) which can inhibit the effects of estrogen in the breast tissue.
  • Toremifene (Fareston) is another SERM that is sometimes used in advanced breast cancer in postmenopausal people.
  • Goserelin (Zoladex) and leuprolide (Lupron) stop estrogen production.
  • Monoclonal antibodies such as trastuzumab (Herceptin, others) and pertuzumab (Perjeta) attach to the HER2 protein to help stop the cancer cells from growing.
  • Antibody-drug conjugates (ADC) such as ado-trastuzumab emtansine (Kadcyla or TDM-1) and fam-trastuzumab deruxtecan (Enhertu) attach to the HER2 protein on cancer cells, bringing any chemotherapy directly to it.
  • Kinase inhibitors such as lapatinib (Tykerb), neratinib (Nerlynx), and tucatinib (Tukysa) attempt to slow cell growth by blocking growth signals from a type of protein called kinase.

Learning the basics of HR-positive/HER2-negative breast cancer makes it easier for you and your loved ones to understand your options and cope with your diagnosis.

In addition to HR and HER2 status, a number of other things will factor into your choice of treatment:

  • Stage at diagnosis. Breast cancer is divided into stages 1 through 4 to indicate tumor size and how far the cancer has spread. Cancer is easier to treat in the early stages, before it has the chance to spread. Stage 4 means the cancer has reached distant tissues or organs. This is also called advanced or metastatic breast cancer.
  • Tumor grade. Breast tumors have a tumor score of 1 to 3. Grade 1 means the cells are close to normal in appearance. Grade 2 means they’re more abnormal. Grade 3 means they bear little resemblance to normal breast cells. The higher the grade, the more aggressive the cancer.
  • Whether this is a first cancer or a recurrence. If you’ve previously been treated for breast cancer, you’ll need a new biopsy and pathology report. This is because your HR and HER2 status may have changed, which will affect the approach to treatment.

As well, your overall health — including other medical conditions, your age and whether you’re pre- or postmenopausal, and personal preferences — will dictate the course of treatment.

Hormonal treatment can be harmful to a fetus if the patient becomes pregnant. If you plan on starting a family or adding to your family, talk to your doctor about this before you start treatment.

Cancer treatment is likely to go more smoothly when you ask questions and communicate openly with your oncology team.