Triple-negative breast cancer (TNBC) is a fast-growing cancer that requires aggressive treatment. The term “triple-negative” means that the breast cancer cells don’t contain three particular proteins that are often found in other types of breast cancer.

About 170,000 people are diagnosed with TNBC throughout the world each year. Out of all breast cancer cases, around 10 percent to 15 percent are triple-negative. Researchers have found that women who are younger than 40, Black, or Hispanic have a higher risk of developing TNBC.

What Is Triple-Negative Breast Cancer?

Breast cancer can be classified in several different ways. One is to describe the type of breast cancer by identifying which cell type originally became cancerous and whether the cancer is invasive (has spread to other areas). Using these criteria, breast cancer may be given names like “ductal carcinoma in situ” or “invasive lobular carcinoma.”

Doctors may also categorize breast cancer by molecular subtype. The molecular subtype refers to proteins that are found inside or on the outside of cancer cells. These proteins receive messages from other parts of the body and tell the cell when to grow and what to do. There are three main proteins that doctors look for when determining the molecular subtype:

• Estrogen receptor (ER)
• Progesterone receptor (PR)
• Human epidermal growth factor receptor 2 (HER2)

ER and PR are types of proteins called hormone receptors. These proteins attach to hormones (molecules that act as signals) that are produced by the body. Breast cancer cells that contain ER or PR rely on hormones to continue growing. Likewise, breast cancer cells that have HER2 on their surface rely on HER2 to grow.

Doctors use the terms “positive” and “negative” to describe a cancer’s status. For example, breast cancer that is hormone receptor-positive contains one or both of the hormone receptor proteins. Researchers have developed drug treatments that can block ER, PR, and HER2. This prevents cancer cells from growing and eventually kills the cells.

When a person’s breast cancer cells don’t contain any of these three proteins, doctors refer to it as “triple-negative.” Because TNBC cells don’t rely on ER, PR, or HER2 to grow, they don’t respond to drugs that block these proteins. This means that TNBC is harder to treat than other types of breast cancer.

Triple-Negative Breast Cancer Risk Factors

TNBC tends to affect women at younger ages than other cases of breast cancer. Among all types of breast cancer, women are diagnosed at an average age of 63. However, TNBC is more likely to affect women under the age of 40.

Black women and Hispanic women are also more likely to be diagnosed with TNBC than white women, according to researchers, but they don’t yet know exactly why this is. However, they believe that both genetic factors and socioeconomic factors may play a role.

Some gene changes, such as mutations in the BRCA genes, can also lead to a high risk of breast cancer. These gene changes are passed down from parent to child. About 70 percent of people with a BRCA gene mutation who are diagnosed with breast cancer have TNBC. If you have a family history of breast or ovarian cancer, there is a chance you may have a BRCA mutation. Ask your doctor about genetic testing for these genes.

Symptoms of Triple-Negative Breast Cancer

TNBC causes similar symptoms as other forms of breast cancer. These may include:

• A hard lump in the breast or armpit
• Swelling of the breast
• Skin changes, such as discoloration, dimpling, or creases
• An inverted nipple
• Nipple discharge in one breast
• Changes in breast appearance
• Breast pain

These symptoms can be caused by many other health conditions besides cancer. In addition, many people who are diagnosed with breast cancer do not have any symptoms at all. Follow your doctor’s advice when it comes to getting screened for breast cancer, and tell your doctor if one or both breasts starts looking or feeling different than normal.

How Do Doctors Diagnose Triple-Negative Breast Cancer?

Breast cancer diagnosis often starts when a person or their doctor notices a lump in the breast, or when a screening test for breast cancer detects unusual breast tissue. After finding a mass, the doctor will perform additional imaging tests, as well as a biopsy.

Several types of imaging tests can capture pictures of the inside of the breast, helping the doctor see whether there are any problems. Imaging tests may include a mammogram, ultrasound, or MRI. An MRI can also help doctors plan for surgery or determine whether cancer cells have spread to other parts of the body.

The only test that can officially diagnose breast cancer is a biopsy. During this test, the doctor uses a needle to remove a small sample of tissue. The tissue is sent to a laboratory, where a pathologist runs tests to determine whether the cells in the sample are cancerous. Laboratory tests can also identify the cancer’s type, molecular subtype, and grade (how abnormal the cancer cells look and how fast they are growing). Doctors use this information to estimate a person’s outlook and know which treatments are likely to work best.

Stages of Triple-Negative Breast Cancer

During the process of diagnosis, doctors will also assign a cancer stage. The stage tells you how far the cancer has spread within the body. Early tumors located in one small spot are stage 0. Advanced TNBC that has metastasized (spread to distant organs or tissues) is described as stage 4 (sometimes in Roman numerals, e.g., stage IV).

Treatment of Triple-Negative Breast Cancer

TNBC is often treated with chemotherapy, surgery, or radiation therapy, or some combination of these options. A person’s treatment plan may be different depending on their disease stage and whether the cancer has relapsed (come back after being treated).

Other types of breast cancer are often treated with other treatments such as targeted therapies and hormone therapies. These drugs block the proteins ER, PR, and HER2. Because triple-negative breast cancer doesn’t contain these proteins, many targeted therapies and hormone therapies will be ineffective.

Chemotherapy and Other Cancer-Fighting Drugs

Most people with TNBC take chemotherapy drugs to help kill cancer cells. Chemotherapy may be given at different points along the treatment journey. Neoadjuvant therapy is given before surgery to shrink a tumor and make it easier to remove. Adjuvant therapy is given after surgery to remove any remaining cancer cells left behind

Many types of chemotherapy drugs are given to people with breast cancer, including TNBC. Platinum-based drugs, including Platinol (cisplatin) and Paraplatin (carboplatin), prevent cancer cells from repairing themselves. These drugs allow damage to build up until the cancer cell dies. Taxane drugs like Taxotere (docetaxel) and Taxol (paclitaxel) prevent cells from growing and dividing. Anthracycline drugs also stop cells from dividing and create damage within a cell. Xeloda (capecitabine) slows down cancer cell growth. Often, these chemotherapy drugs and others are given together in different combinations.

Targeted therapy or immunotherapy drugs may be available for people with certain gene mutations or for those who have been diagnosed with advanced TNBC:

• People with changes in the BRCA genes may be able to take drugs called PARP inhibitors, including Talzenna (talazoparib) or Lynparza (olaparib).
• If a person’s cancer cells make a protein called PD-L1, they may be able to take the immunotherapy drug Keytruda (pembrolizumab).
• People with metastatic disease who have already tried other chemotherapy drugs may be able to receive Trodelvy (sacituzumab govitecan-hziy).

Surgery

Many people with TNBC undergo surgery to remove the breast cancer, although this may not be an option for people with stage 4 metastatic cancer. If the tumor is small and located in just one part of the breast, a lumpectomy may be an option. During this surgery, doctors remove cancer cells and a small amount of surrounding healthy breast tissue. If the tumor is larger or has spread further throughout the breast, surgeons may need to perform a mastectomy, in which all of the breast tissue is taken out.

In many cases, people with TNBC will need surgery to remove one or more lymph nodes. Lymph nodes are small structures that help filter out waste and foreign particles from the body. When a tumor develops, cancer cells often collect in nearby lymph nodes. Surgically removing the lymph nodes helps doctors see whether cancer cells have begun to spread, which helps them determine staging and make treatment decisions.

If one, two, or three lymph nodes are taken out, the procedure is called a sentinel lymph node biopsy. When doctors remove many lymph nodes, the surgery is called an axillary lymph node dissection.

Radiation Therapy

After surgery, some people with TNBC receive radiation therapy, in which high-energy particles or beams are directed at the breast and surrounding area. Radiation treatments can help damage and kill any surviving breast cancer cells. This may be especially helpful for people with BRCA1 mutations. When cancer cells lack this gene, they are less likely to be able to repair damage and survive.

Clinical Trials

Researchers have been looking for other possible treatment options for TNBC. They have identified other gene changes that often occur in TNBC cells, and they’re looking for other drugs that may be able to target these gene changes.

Researchers study whether new drugs are safe and effective — and test new drug doses and treatment plans — using clinical trials. People with TNBC may be able to access new treatment options by participating in clinical trials.

Triple-Negative Breast Cancer Prognosis

TNBC often leads to a poor prognosis (outlook). This type of cancer is often hard to treat. TNBC is more likely to metastasize and relapse.

People with TNBC are 77 percent as likely to live for at least five years after they are diagnosed compared to people without the disease. However, survival rates vary widely based on the breast cancer stage:

• People with TNBC that is only growing within one small area are 91 percent as likely to live for five years or more once they receive their diagnosis.
• People with TNBC that has begun to grow into surrounding tissues are 65 percent as likely to live at least five years.
• People with metastatic TNBC, who have had cancer cells spread to other areas outside the breast and chest, are 12 percent as likely to live at least five years, compared to others without TNBC.

Breast cancer survival rates are constantly improving as researchers develop better treatments. The above survival rates were calculated using data from people diagnosed with breast cancer between the years of 2010 and 2016. People being diagnosed today may have better survival rates.

Other factors also play a role in outlook. People who are at least 65 years old are more likely to have a poor outcome from TNBC. Other factors that may lead to a worse prognosis include having other health conditions, having a higher tumor grade, or having cancer cells in the lymph nodes. Factors that may lead to a better outcome for people with TNBC include high levels of platelets and low levels of CA15-3 (a protein made by breast cancer cells).

If you are interested in learning more about your own prognosis, talk to your health care team. Your doctor can explain how your individual factors affect your outlook and help you understand what to expect.

Talk With Others Who Understand

MyBCTeam is the social network for people with breast cancer and their loved ones. On MyBCTeam, more than 53,000 members come together to ask questions, give advice, and share their stories with others who understand life with breast cancer.

Are you living with triple-negative breast cancer? Share your experiences in the comments below, or start a conversation by posting on MyBCTeam.