What Is Triple-Negative Breast Cancer?
Key takeaways:
Triple-negative breast cancer is an aggressive form of breast cancer.
Treatment may include surgery, radiation therapy, chemotherapy, and/or immunotherapy.
The prognosis for triple-negative breast cancer depends on the cancer’s stage.
Triple-negative breast cancer is a subtype of breast cancer. It makes up about 10% to 15% of breast cancer cases.
Breast cancer cells are often tested for three surface receptors: the estrogen receptor, the progesterone receptor, and the HER2 receptor. Breast cancer is “triple negative” when the cancer cells don’t have any of these receptors.
How is triple-negative breast cancer different from other types of breast cancer?
Triple-negative breast cancers tend to be aggressive. They grow quickly, and the cells are usually high grade. This means they look very different from normal breast cells. Triple-negative breast cancer is also more likely than other breast cancers to metastasize (spread) to other parts of the body.
Many breast cancer treatments don’t work in triple-negative breast cancer. For example, medications like tamoxifen work on the estrogen receptor. Similarly, trastuzumab works on the HER2 receptor. Since triple-negative breast cancers don't have these receptors, these medications don’t work.
For these reasons, triple-negative breast cancer is harder to cure than other breast cancers.
What are the symptoms of triple-negative breast cancer?
The symptoms of different breast cancers are the same. In other words, triple-negative breast cancers generally have the same symptoms as other breast cancers.
Breast cancer is often found on a screening mammogram. In these cases, the person often doesn’t have any symptoms. In other cases, a person may feel a lump in the breast or in the lymph nodes under the arm.
When breast cancer has spread to other parts of the body, the symptoms depend on where the cancer is located. For example, cancer that has spread to the bones often causes pain.
How do you diagnose triple-negative breast cancer?
When a person has an abnormal mammogram or a lump in the breast, the next step is usually more imaging. Imaging tests may include more mammograms, ultrasounds, or MRI scans.
If the imaging suggests breast cancer, the next step is a biopsy. A provider will take a sample of the tissue and look at it under the microscope.
When a biopsy shows cancer, more tests are done on the tissue. These tests include checking for the estrogen, progesterone, and HER2 receptors. If none of these receptors are present, the cancer is called “triple negative.”
How do you treat triple-negative breast cancer?
The treatment for triple-negative breast cancer depends on the stage. Options include surgery, chemotherapy, immunotherapy, and radiation therapy.
Surgery
If the cancer is in stages 1 to 3, the primary treatment is surgery. This can be a mastectomy (removal of the whole breast) or a lumpectomy (removal of the tumor). The surgeon usually performs a lymph node biopsy at the same time.
Chemotherapy
Surgery is the main treatment for triple-negative breast cancer. But chemotherapy is used to prevent the cancer coming back.
Chemotherapy can be given before or after surgery, depending on the stage of triple-negative breast cancer:
Stage 1: It’s more common to give chemotherapy after surgery.
Stages 2 to 3: Chemotherapy is often used before surgery. This helps to better understand how well the cancer responds to the chemotherapy. This helps select the best chemotherapy treatment for after surgery.
Chemotherapy medications for triple-negative breast cancer include doxorubicin, carboplatin, paclitaxel, docetaxel, and cyclophosphamide.
Immunotherapy
Immunotherapy is a treatment that helps the immune system identify and kill cancer cells. Like chemotherapy, immunotherapy can also help to shrink tumors before surgery.
The only approved immunotherapy for triple-negative breast cancer is pembrolizumab. This is an immune checkpoint inhibitor.
In stage 1 to 3 triple-negative breast cancer, immunotherapy can be used to shrink a tumor before surgery.
In stage 4 breast cancer, immunotherapy is often combined with chemotherapy. For some people, adding immunotherapy to chemotherapy improves outcomes.
A recent clinical trial studied immunotherapy treatment in women with advanced triple-negative breast cancer. Half of the group got chemotherapy, and the other half got both chemotherapy and immunotherapy. On average, it took longer for the cancer to advance in the people who got immunotherapy.
Immunotherapy’s side effects are different from those of other cancer medications. The most common ones are fatigue, rash, and diarrhea.
Radiation
After surgery for triple-negative breast cancer, most people also get radiation therapy. The goal of radiation therapy is to prevent the cancer from coming back. It’s a standard treatment after a lumpectomy. Depending on the surgery’s findings, some people also get radiation after a mastectomy.
When breast cancer spreads to other parts of the body, it’s in stage 4. The primary treatments for stage 4 triple-negative breast cancer are chemotherapy and immunotherapy. People who have a BRCA1 gene mutation may also get a PARP inhibitor medication.
How serious is triple-negative breast cancer?
Compared to other subtypes of breast cancer, triple-negative breast cancer has a worse prognosis. This means it’s more likely to grow quickly and come back in the first few years after treatment.
But the prognosis for triple-negative breast cancer depends on the cancer’s stage and its response to chemotherapy (if given before surgery). Stage 1 to 3 cancers may often be cured with treatment. This is especially true if there’s a “complete response” to preoperative chemotherapy. This means that no surviving cancer cells were found at the time of surgery.
Can triple-negative breast cancer metastasize?
Metastasis is when cancer spreads from its original site to another part of the body. When breast cancer metastasizes, it’s in stage 4. In triple-negative breast cancer, about 6% of cases are in stage 4 when they’re diagnosed.
Stage 4 triple-negative breast cancer is not curable, and the prognosis is poor. Still, treatment may help people to live longer and have fewer symptoms from their cancer.
The bottom line
Triple-negative breast cancer is an aggressive type of breast cancer. The treatment and prognosis for triple-negative breast cancer depend on the cancer’s stage. Surgery, chemotherapy, immunotherapy, and radiation therapy all play a role in treatment.
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References
American Cancer Society. (2021). Breast cancer hormone receptor status.
American Cancer Society. (2022). Breast cancer HER2 status.
American Cancer Society. (2023). Triple-negative breast cancer.
Cortes, J., et al. (2020). Pembrolizumab plus chemotherapy versus placebo plus chemotherapy for previously untreated locally recurrent inoperable or metastatic triple-negative breast cancer (KEYNOTE-355): A randomised, placebo-controlled, double-blind, phase 3 clinical trial. The Lancet.
MedlinePlus. (2020). BRCA1 gene.
National Cancer Institute Dictionary of Cancer Terms. (n.d.). PARP inhibitor.
National Cancer Institute. (2022). Immune checkpoint inhibitors.
Plasilova, M. L., et al. (2016). Features of triple-negative breast cancer: Analysis of 38,813 cases from the national cancer database. Medicine.
