Triple-Negative Breast Cancer (TNBC) Explained

When breast cancer is diagnosed, the tissue is tested for three things. These are the estrogen receptor (ER), the progesterone receptor (PR), and a protein called HER2. When all three come back negative, the cancer is called triple negative.

The name says what the cancer lacks. It does not say how serious it is. But it matters. Hormone-blocking pills such as tamoxifen and aromatase inhibitors latch onto the hormone receptors. HER2 drugs such as trastuzumab latch onto HER2. If none of those targets is there, those pills cannot help. Other tools do the work instead. Those are chemotherapy, immunotherapy, surgery and radiation. Triple-negative disease often responds well to chemotherapy.

Triple-negative disease makes up roughly 10 to 15 percent of breast cancers. It is found more often in Black women. It is also more common in women under 40, and in people who carry an inherited BRCA1 mutation. It tends to grow faster than hormone-receptor-positive cancer. When it comes back, it usually comes back in the first few years. It is less likely to return a decade later.

The higher rate in Black women is not only biology. Access to screening differs. So does the wait from an abnormal scan to a biopsy. So does how fast treatment starts. That is worth naming. Delays are something a care team and a patient can push back against.

Ask for genetic counseling and testing. They are advised for everyone with triple-negative breast cancer, whatever your family history. A BRCA1 or BRCA2 mutation can change which surgery you pick. It also opens up PARP inhibitors such as olaparib or talazoparib. And it gives your relatives facts they can act on. Ask for the referral early. Results can take several weeks.

Some tumors are larger than about 2 centimeters. In others, the lymph nodes are involved. In both, chemotherapy is usually given before surgery. This is called neoadjuvant treatment. It can shrink the tumor enough to allow a smaller operation. It also shows your team whether the cancer is responding while you are still being treated.

For high-risk stage II and III disease, pembrolizumab is added to that chemotherapy. Pembrolizumab is an immunotherapy drug. It is then kept going after surgery. In trials, this raised the number of people whose tumors went away completely. It also improved event-free survival.

At surgery, the removed tissue is examined. Say no invasive cancer is left. That is a pathologic complete response, and it is linked to better long-term outcomes. Say some cancer is left. That is not a failure. It tells your team that more treatment after surgery is worth giving. That may be a different chemotherapy drug. Or it may be a PARP inhibitor, if you carry a BRCA mutation.

Radiation is often advised after lumpectomy. It is sometimes advised after mastectomy too. That depends on tumor size and lymph nodes.

Once triple-negative breast cancer has spread, the aim shifts. Now the goal is to hold it in check for as long as possible. Quality of life is protected at the same time. Options include:

• Chemotherapy. Often one drug at a time, which limits side effects.
• Pembrolizumab with chemotherapy. This is used when the tumor has enough PD-L1 expression.
• Sacituzumab govitecan. This is an antibody-drug conjugate. It carries chemotherapy to cells that show the Trop-2 protein.
• PARP inhibitors such as olaparib or talazoparib. These are for people with an inherited BRCA1 or BRCA2 mutation.
• Clinical trials. In this subtype they are often worth weighing at every decision point, not just at the end.

Treatment usually goes on until it stops working, or until side effects get too heavy. Then it is changed. Living with metastatic disease over years is more and more common. Palliative care alongside treatment helps with pain, fatigue and sleep.

Ask for your full pathology report and keep a copy. Write down which chemotherapy drugs you have had. That determines what comes next. Three side effects are the most likely to need a dose change. They are fatigue, neuropathy (nerve damage that causes numbness or tingling) and low blood counts. Report them early. That usually keeps treatment on track rather than stopping it.

• Call 911 or go to an emergency department if you cannot catch your breath, your chest hurts, or your heartbeat turns irregular while on pembrolizumab. Also go now for bleeding that will not stop, or for widespread blistering or peeling of the skin.
• Call your care team this minute, day or night, if your temperature hits 100.4°F (38°C) or higher, or you get chills and feel unwell during chemotherapy. The CDC calls this a medical emergency, because with low blood counts an infection can move within hours. If they cannot be reached fast, go to an emergency department and lead with the fact that you are on chemotherapy.
• Call your care team the same day if you have several loose stools more than usual in a day, blood or black tarry material in your stool, or bad belly pain while on immunotherapy. Immune-related inflammation of the bowel is treatable, and treated sooner it is milder.
• Call your care team within a day or two if numbness or tingling in your hands or feet is new or spreading, or if the whites of your eyes look yellow. Reporting neuropathy early is what lets your team adjust the dose instead of stopping the drug.

• NCI: Breast Cancer Treatment (PDQ®) Patient Version
• American Cancer Society: Triple-Negative Breast Cancer
• NCI drug information: sacituzumab govitecan-hziy
• NCI drug information: olaparib
• NCI: BRCA Gene Mutations Fact Sheet
• MedlinePlus: Pembrolizumab Injection
• CDC — Fever and Cancer Treatment
• NCI: Infection and Neutropenia during Cancer Treatment