Breast cancer has seen amazing improvements in survival rates thanks to research. But there are many different types of breast cancer and not all have benefitted from these breakthroughs. Triple negative breast cancer (TNBC) is a particularly aggressive type of breast cancer for which more research is urgently needed.
What is triple negative breast cancer?
Not all breast cancers are alike – in fact, when breast cancer is diagnosed and a biopsy is taken, the cells will be tested to understand what kind of breast cancer a patient has. Breast cancer cells can have receptors on the outside which are sensitive to different proteins which help the cancer grow.
These proteins include the hormones oestrogen and progesterone, as well as a protein called HER2. Understanding if a breast cancer has these receptors helps doctors decide the best treatment for patients.
Triple negative breast cancer (TNBC) cells don't have any of these receptors. Because the TNBC cells test negative for these three receptors and don’t grow in response to hormones or HER2, they are 'triple negative'.
A particularly aggressive type of cancer, TNBC affects roughly 1 in 5 women with the disease, and it tends to be more common in younger people under the age of 40, as well as Black and Hispanic people.
What causes triple negative breast cancer?
Like all types of breast cancer, anybody can be diagnosed with TNBC, and the causes are similar to those of other breast cancer types. The risk of getting breast cancer can increase with factors like alcohol consumption, smoking, or living with obesity.
For TNBC in particular, inherited genetics do play a role and TNBC can run in families. People with mutations in their BRCA1 or BRCA2 genes are more likely to develop certain types of cancer, including breast cancer. About 70% of breast cancers diagnosed in people with a BRCA mutation are TNBC and BRCA1 seems to play a bigger role than BRCA2 mutations.
Overall, a person has a higher risk of developing TNBC if they:
- Are Black or Hispanic
- Are under 50 years old
- Have a BRCA mutation
- Are not breastfeeding
- Are obese or overweight
- Have high breast density
How is triple negative breast cancer diagnosed and treated?
Like other breast cancer types, TNBC is often found during breast screening. Most diagnoses will involve a referral to a specialist breast clinic and potentially mammograms, ultrasounds and a biopsy.
During a biopsy, a sample is taken from the tumour and analysed to check for oestrogen receptors, progesterone receptors and HER2 protein – if all three tests come back negative, the diagnosis is usually TNBC.
TNBC is most commonly treated with a combination of surgery, radiotherapy and chemotherapy, but some patients can benefit from immunotherapy. Atezolizumab, the first immunotherapy available on the NHS for certain types of TNBC, helps the immune system to attack cancer cells by blocking an immune system break called PD-L1.
Other promising new therapies include PARP inhibitors, such as olaparib, which are already available in the US for certain types of breast cancer with BRCA mutations.
What makes triple negative breast cancer less survivable?
Unfortunately, TNBC tends to spread earlier and faster to other organs, such as the brain, lung, liver and bones, than other types of breast cancer, and it tends to be a higher grade of tumour when detected. As TNBC is lacking the proteins that are targeted by hormonal and targeted therapies, the treatment options are more limited
TNBC can also quickly become resistant to treatments, and unfortunately it is more likely than other types of breast cancer to come back after treatment, within the first 4 years of diagnosis.
While TNBC can be treated, it is still one of the more challenging breast cancers to cure and so more research is needed to understand how it develops and how to treat it.
We’re funding international cancer research supporting scientists who are working on understanding TNBC better, so that fewer lives are cut short by this aggressive disease:
- Dr Hector Peinado in Spain is investigating how living with obesity can make it easier for TNBC to grow and spread. We know that obesity can increase the risk of several types of cancer, but there still isn’t a clear explanation of how it makes it easier for cancers like TNBC to spread. Dr Peinado and his team want to uncover the mechanism behind this to help develop methods to stop TNBC from spreading, and from coming back after treatment.
- Dr Klaus Pors at the University of Bradford is working with researchers in South Africa to develop a new treatment for TNBC. He and his collaborators are investigating a new approach to targeting TNBC, by engineering proteins that can find and stick to TNBC cancer cells. This “Trojan horse” method could be a way to deliver toxic drugs to the cancerous cells while leaving healthy cells alone, resulting in a more effective treatment with fewer side effects.
While advanced TNBC is still seen as an incurable disease, new treatment options are starting to change this status quo. By funding more research, our Curestarters can help find new cures for triple negative breast cancer.
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