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Cancer explained

Triple negative breast cancer – Everything you need to know

1st October 2021

Breast cancer is a type of cancer which has seen amazing improvements in survival rates thanks to advances in early detection, diagnosis, and treatment. But there are many different types of breast cancer and not all have benefitted from the research breakthroughs that are saving lives. Triple negative breast cancer (TNBC) is a particularly aggressive type of breast cancer for which more research is urgently needed. Here’s everything you need to know about TNBC.

What is triple negative breast cancer?

Triple negative breast cancer is an aggressive type of breast cancer that affects about 8,000 people in the UK every year. Roughly 1 in 5 women with breast cancer have TNBC and it tends to be more common in younger people under the age of 40, as well as Black and Hispanic people.

Unfortunately, TNBC is also more likely to spread to other organs, such as the brain, lung, liver and bones, than other types of breast cancer. TNBC also tends to be a higher grade of tumour when detected, which means that its cancer cells look and behave very differently from normal breast cells.

TNBC cells neither have receptors for the hormones oestrogen or progesterone nor the protein HER2. Because the TNBC cells test negative for these receptors and don’t grow in response to hormones or HER2, they are “triple negative”.

 

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What causes triple negative breast cancer?

While anyone can be diagnosed with triple negative breast cancer, 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
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How is triple negative breast cancer diagnosed and treated?

Triple negative breast cancer is often found during breast screening and has similar symptoms to other types of breast cancers, such as lumps or changes to the breast. 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. 

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What makes triple negative breast cancer worse than other breast cancers?

Triple negative breast cancer tends to spread earlier and faster than other types of breast cancer. As TNBC is lacking the proteins that are targeted by hormonal and targeted therapies, the treatment options are more limited. Unfortunately, TNBC also has the highest likelihood of recurrence, or coming back, within the first 5 years after diagnosis. While advanced TNBC is still seen as an incurable disease, new treatment options, such as immunotherapy and PARP inhibitors, are starting to change this status quo.

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