Metastatic Triple Negative Breast Cancer (mTNBC)

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.


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