What is Metastatic Breast Cancer?

Metastatic breast cancer occurs when breast cancer cells travel from the breast to another part of the body such as the bones, liver, lungs, or brain. Metastatic breast cancer is also referred to as Stage IV breast cancer.

A second breast cancer that develops in the same or the other breast is not metastatic breast cancer. And having cancer cells in the lymph nodes does not mean your cancer is Stage IV, although pathologists sometimes use the term "metastatic to the lymph nodes."

What does it mean to have metastatic breast cancer?

A diagnosis of metastatic breast cancer can be very frightening because it is considered to be incurable. But as treatments improve, metastatic women are living longer and able to have better quality of life. Living with metastatic breast cancer usually involves ongoing treatment -- chemotherapy, hormonal treatment, or radiation.

When is metastatic breast cancer usually diagnosed?

Some women (about six percent) are initially diagnosed at Stage IV. They may already have symptoms such as pain or shortness of breath that cause the doctors to suspect metastatic cancer. Or the metastasis may be discovered during a CT or PET scan as part of the initial workup for breast cancer.

Most women who become metastatic are diagnosed later, anytime from several months to years after they were initially treated for early stage cancer.

What causes metastatic breast cancer?

We still do not understand why some cancers become metastatic, especially those that are diagnosed years after the first breast cancer. In the past, doctors believed that cancer progressed in a linear manner and that women with positive lymph nodes were more likely to become metastatic. Now researchers are focusing more on genetics and the microbiology of breast cancer. They are trying to learn why some cancers behave more aggressively, what causes cancer cells to grow in different parts of the body, and what treatments can be developed to stop that process.

Subtypes of Metastatic Breast Cancer

Individuals with breast cancer are referred to as having metastatic triple-negative breast cancer disease when tumors have spread outside of the breast and lymph nodes and the cancer tumor does not have the three common breast cancer receptors, estrogen receptor, progesterone receptor or human epidermal growth factor receptor.

How is Metastatic Triple Negative Breast Cancer Diagnosed?

Bone Scan: A scan that uses a radiotracer to look for the spread of cancer in the bones.

Magnetic Resonance Imaging (MRI) Scan: A scan that uses radio waves, a powerful magnet, and a computer to make a series of detailed pictures of areas inside the body to detect presence and size of a tumor.

Computerized Tomography (CT) Scan: A scan that uses a computer linked to an x-ray machine to make a series of detailed 3-D pictures of areas inside the body to look for cancer that has spread outside the breast such as liver, lungs and bone. May or may not use contrast.

Positron Emission Tomography (PET Scan): A scan in which a small amount of radioactive glucose (sugar) is injected into a vein, and a scanner is used to make detailed, computerized pictures of areas inside the body where the glucose is taken up to locate the presence of cancer that has spread outside of the breast. This scan is used along with a CT scan.

Biopsy: The removal of cells or tissues by a surgeon or interventional radiologist for examination by a pathologist. A pathologist will test the breast cancer cells to measure the presence of estrogen (ER) or progesterone (PR) receptors and human epidermal growth factor (Her2) receptor proteins using special stains on the tumor specimen called immunohistochemistry (IHC) or in situ fluorescent hybridization (FISH).

  • The cancer is considered ER/PR negative when the cells examined shows that less than 1% have estrogen and/or progesterone receptors.
  • The cancer is considered HER2-negative when the HER2 result shows a score of 0 or 1+.
  • If the HER2 result has a score of 2+, the HER2 status of the tumor is not clear and is called "equivocal." This means that the HER2 status needs to be tested with FISH to clarify the result.
  • The cancer is considered Her2-low when the cancer has been classified as Her2-negative with results showing a score of 1+ or 2+. While Her2-low is still considered Her2- the Her2-low designation can open up treatment options for many patients.

How is Triple Negative Breast Cancer Treated?

NCCN guidelines recommend genetic testing and biomarker testing as the results may open up treatment options.

  • BRCA 1/2 mutation- A Parp inhibitor such as Olaparib (Lynparza) may be considered.
  • PDL-1 protein overexpression - treatment may include immunotherapy such as pembrolizumab (KEYTRUDA) plus chemotherapy.
  • HER2- low where IHC test revealed (1+,2+) - a Her2 directed antibody drug conjugate (ADC) Trastuzumab deruxtecan(t-dxd) (Enhertu) may be used Approximately 30-35% TNBC are considered Her2- low.
  • Antibody Drug Conjugate (ADC) Sacituzumab Govitecan (Trodelvy) may be used as TNBC cells have Trop2 on them. Sacituzumab attaches to the Trop2 protein and delivers the medicine to destroy the breast cancer cells. Sacituzumab has a “bystander” effect which means it destroys neighboring cancer cells.
  • Chemotherapy is a systemic treatment that goes throughout the body and is used to destroy cancer cells and prevent them from dividing. The treatment can be in the form of an oral medicine like capecitabine (Xeloda) or an IV medicine like cisplatin, carboplatin or gemcitabine (Gemzar).

Clinical Trial Information:

TNBC disproportionately affects Black women, Hispanic women, and younger women as well as individuals who carry a BRCA1 gene mutation. Please see below resources that may be of benefit to you.


Where can I get more information about metastatic breast cancer?

Call SHARE's Metastatic Breast Cancer Helpline. Our breast cancer helpline has trained metastatic peers ranging in age from early thirties to eighty. Some have been living with metastatic disease for many years. We can answer your questions, help you figure out your options, and give you realistic hope and support. Call us at 844-ASK-SHARE (844-275-7427).

Our bi-monthly e-newsletter provides information for women living with metastatic breast cancer.

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