Triple-negative breast cancer is a subtype of breast cancer in which the cancer has tested negative for the following markers:
- HER2 protein
- Estrogen receptors
- Progesterone receptors
Approximately 10 to 15 percent of breast cancers are triple-negative. Black women, younger women, and those with a BRCA1 gene mutation are more likely to develop this type of disease, according to the American Cancer Society.
Triple-negative breast cancers have historically been more aggressive and more challenging to treat, in part because the disease is aggressive, and in part because many available therapies target the proteins and receptors they lack. As a result, the disease is at higher risk of recurring or spreading beyond the breast. But every case is different, and your prognosis will depend on many factors.
What Causes Triple-Negative Breast Cancer?
It’s not clear why some breast cancers don’t have those three markers, but researchers believe a mutation in the BRCA1 gene might have something to do with it. The BCRA1 gene is supposed to help keep cancer from developing, but if there’s a mutation, it’ll do the opposite.
As mentioned above, Black women and younger women — women under 40, but also under 50 — are more likely to be diagnosed with this kind of cancer. Black women are diagnosed with this cancer at 2 to 3 times the rate of white women, per studies published in Breast Cancer Research and Cancer Medicine.
Researchers aren’t sure exactly why Black women experience increased rates of diagnosis, but they think both genetics and socioeconomic factors may play a role, according to research published in Cancers.
How Is Triple-Negative Breast Cancer Diagnosed?
If mammogram results suggest there might be cancer, you’ll undergo a biopsy. In a biopsy, a tissue sample is removed from the breast and examined to confirm whether cancer has developed. Core needle biopsies, in which breast tissue is excised through a needle, are the most common type of biopsy and are the standard of care. They’re performed by radiologists or surgeons.
If the suspicious area can’t be reached by a core needle biopsy, or results from a core needle biopsy are unclear, a surgeon will perform a surgical biopsy. In surgical biopsies, all or part of the possibly cancerous tissue or tumor will be removed.
If the sample is found to be cancerous, it will be tested to see if it is HER2-positive and has either or both estrogen or progesterone receptors. In order to do this, your doctor will use the following:
- Immunohistochemistry (ICH) Test This is used to measure the amount of HER2 protein on the cancer cells and can also detect estrogen and progesterone receptors.
- Fluorescence in Situ Hybridization (FISH) Test This test can assess how many copies you have of the HER2 gene. It’s usually given in addition to an IHC test if the IHC results are unclear.
What Are the Stages of Triple-Negative Breast Cancer?
The terms “stage” and “staging” can be used in a variety of ways when talking about breast cancer diagnosis and treatment.
There’s a numerical staging system that’s commonly used to give a description of how large the tumor is and how far the cancer has spread. These are the five stages of breast cancer: stage 0, stage 1, stage 2, stage 3, or stage 4. The lower the number, the smaller and more localized the cancer will be.
Triple-negative does not occur at a specific stage. The term describes the nature of the tumor.
However, the tests for HER2 status and hormone receptor status — the tests needed for a diagnosis of triple-negative — are typically not administered if the cancer is stage 0 (or noninvasive) breast cancer.
What Is Metastatic Triple-Negative Breast Cancer?
Stage 4 cancer is metastatic cancer. In metastatic cancer, the disease has spread from beyond the breast to other parts of the body.
In metastatic triple-negative breast cancer, as with all metastatic breast cancers, the cancer has spread from beyond the breast to other parts of the body, such as the lungs, liver, brain, or bones. More than one-third of triple-negative patients experience metastasis, notes an article published in ESMO Open.
What Is the Treatment for Triple-Negative Breast Cancer?
Because triple-negative cancer does not have hormone receptors or the HER2 protein, it won’t respond to hormonal therapy or HER2-positive targeted therapies, which, along with surgery and chemotherapy, are some of the most commonly used treatments for breast cancer.
The treatment you receive will depend on how advanced the cancer is and whether it’s recurrent.
Treatment for triple-negative breast cancer can include one or more of the following:
- PARP inhibitors
Most triple-negative breast cancer treatment involves chemotherapy.
If the cancer is stage 1, it’s usually early enough to address with surgery, followed by chemo or radiation.
If the cancer is in stages 2 to 3, chemo will most likely be administered first, before surgery, to shrink the tumor, but each case is different, and you and your doctor will work together to come up with a treatment plan that will address your particular situation.
In some cases, chemotherapy and the immunotherapy drug pembrolizumab (Keytruda) may be used before and after surgery. Keytruda, like chemotherapy, is administered via IV. It’s used when the cancer cells are determined to contain a protein called PD-L1. The PD-L1 protein is found in 1 out of 5 triple-negative breast cancers, according to a study published in Cancer Immunology Research.
If the cancer is stage 4, or metastatic, the first-line treatment is chemotherapy. Keytruda may also be used.
For some treatment-resistant metastatic cancer, a medication called sacituzumab govitecan-hziy (Trodelvy) may be used. It’s a combination of chemotherapy and another drug that targets the cancer, and is administered via IV.
If you have metastatic triple-negative cancer that’s tested positive for BRCA1 or BRCA2 gene mutations, treatment could also involve drugs known as PARP inhibitors (olaparib and talazoparib). PARP is a protein that helps cells, including cancer cells, repair themselves if they’re damaged. BRCA1 and 2 mutations already make cell repair hard, and these drugs, which keep the protein from doing its job, lead to cancer cell death.
What Are the Survival Rates for Triple-Negative Breast Cancer?
Life expectancy can be affected by the stage of your cancer at diagnosis.
According to the National Cancer Institute, the overall five-year survival rate for triple-negative breast cancer is 77 percent. This means that 77 percent of women diagnosed with this cancer subtype will still be alive five years after diagnosis.
When broken down by how far the cancer’s spread, the five-year survival rates are:
- Localized: 91 percent
- Regional: 65 percent
- Distant: 12 percent
"Localized" means that the cancer is only in the breast; "regional" means that it’s spread to nearby lymph nodes, tissues, and organs; "distant" refers to metastatic cancer, which means it’s spread beyond the breast.
Compared with cancer that tests positive for hormone receptors, triple-negative breast cancer has a worse prognosis. According to a review in the Journal of Hematology and Oncology, it's been estimated that more than 50 percent of patients will have recurrence in the first three to five years after a diagnosis, and patients tend to survive a little over 10 months on the therapies currently available.
Is There a Triple-Negative Breast Cancer Vaccine?
This type of cancer is thought to be a good candidate for a vaccine, as it’s one of the few cancers that triggers an immune response in the body. Researchers are hoping to harness this reaction and train it to help prevent the cancer from developing or returning, or to treat existing tumors.
No vaccine has been approved yet by the U.S. Food and Drug Administration, but there are dozens of clinical trials underway.
Are There Clinical Trials for Triple-Negative Breast Cancer?
Some people with breast cancer can choose to participate in clinical trials and undergo therapies that aren’t yet available to the public. This will help researchers determine whether new treatments are safe and effective.
There are hundreds of clinical trials currently ongoing for triple-negative breast cancer. You can visit ClinicialTrials.gov to see if there are any in your area that are still recruiting.