“I want to be defined by what I am, not by what I am not” – Dr Steven Isakoff (Breast Oncologist).
It’s time to focus on Triple Negative Breast Cancer (TNBC). As summed up by Dr Isakoff, TNBC has been defined by not what it is, but what it isn’t. So what is it not? TNBC means the growth of the cancer does not involve oestrogen, progesterone (hormones often associated with breast cancer) receptors and HER2 receptors. Most recent treatments have been developed for breast cancer with these receptors. This has meant TNBC has had limited treatment options, namely surgery and chemotherapy. However, recent developments in research have allowed for a better understanding of TNBC and opened doors for new treatment options.
“From my perspective, this means there is a huge amount of hope. We are clearly improving the treatments in early TNBC. And it clearly seems to me we are improving outcomes and cure rates.” – Dr Peter Schmid, Chair in cancer medicine at Barts Cancer Institute, Queen Mary University of London.
Here we are going to explain the characteristics of triple negative disease, the treatments that are commonly used, as well as newly approved treatments and potential therapies currently undergoing clinical trials.
How common is TNBC?
TNBC represents approximately 10-15% of all diagnosed breast cancers1,2, with over 8,000 cases diagnosed every year in the UK3. This type of breast cancer seems to be more common in African4,5 and Latina women6, as well as in women under 407,8.
Triple negative breast cancer is often genetically determined and appears to run in families9. The most common genes that have been found to impact the person’s chances to develop breast cancer are BRCA1 and BRCA2 genes. BRCA stands for breast cancer susceptibility gene. Among people with this TNBC, 35% have the BRCA1 genetic variant and 8% the BRCA2 variant, whereas less than 10% of all newly diagnosed breast cancer patients carry these genetic variants10.
Did you know? The NHS offers genetic testing for BRCA1 and BRCA2 gene variants to women under 50 with triple negative breast cancer, including those with no family history of breast or ovarian cancer11.
For more information about familiar risk and breast cancer genetic mutations, head to our previous blog on BRCA.
What can your pathology report tell you about TNBC?
The analysis of your tissue sample from a biopsy or surgery will indicate that your tumour does not express oestrogen receptor (ER), progesterone receptor (PR) or human epidermal growth factor 2 (HER2). In your pathology results, you may read about the percentage of cells being positive for oestrogen and progesterone. If this percentage is less than 1%, the cancer is considered to be hormone receptor-negative. For the HER2 protein, the result would be rated as 0, 1+, 2+ to be considered HER2-negative12.
Triple negative cancer cells tend to look very different from normal breast cancer cells, which means that the cancer is classified as high grade (e.g. grade 3). Cells that behave in this way tend to have high levels of markers that indicate cell proliferation such as Ki67, p53+ and p63+. This means that the cells grow and divide quickly13.
Recently, testing of the protein PD-L1 (anti-programmed cell death-ligand 1) has been approved in the NHS for TNBC patients14. This protein is located on the surface of some cancer cells. PD-L1 protein is recognised by a receptor (PD-1) on the surface of a type of immune cell (T-cell). The immune system is the defense system of the body that protects us against pathogens and disease. Recent research has shown that if PD-L1 is blocked, these immune cells will recognise cancer cells as foreign and would attack them15. Triple negative patients that are PD-L1 positive may benefit from newly developed therapies (see section below).
To better understand your pathology results, head to our previous pathology report blog.
We have pulled together all the different treatment options for triple negative breast cancer that are available on the NHS. We have classified them into three types: chemotherapy, PARP inhibitors and immunotherapy. In this blog, we are going to identify them all, explain how each work and whether or not they have been approved by the National Institute for Health and Care Excellence (NICE), or by its Scottish counterpart (SIGN).
NICE is the British organisation that reviews new and existing drugs. In Scotland, NICE guidelines are not applied. They have the Scottish Medicines Consortium (SMC) and Scottish Intercollegiate Guidelines Network (SIGN) which approve new drugs and create guidelines, respectively. Therefore, the drugs available in NHS Scotland might differ slightly to those in England16.
Chemotherapy is a treatment that uses anti-cancer drugs to target and kills fast-dividing cells in the body. It works by interfering with the cancer cells’ ability to divide and grow. It can be provided before surgery (neoadjuvant) or after surgery (adjuvant).
Chemotherapy before surgery
Neoadjuvant chemotherapy containing both platinum and anthracycline drugs is the treatment now offered to triple-negative invasive breast cancer patients within the NHS11.
- Platinum chemotherapy drugs include cisplatin, carboplatin and oxaliplatin.
- Anthracyclines chemotherapy drugs include doxorubicin (Adriamycin®), epirubicin (Ellence®), doxorubicin (Doxil®), daunorubicin (Cerubidine®), mitoxantrone (Novantrone®).
This therapy can reduce the size of cancer and improve the chances of cancer disappearing in both the breast and lymph nodes in the armpit. However, platinum-based chemotherapy can produce severe side effects. This includes anaemia which means you have a low number of red blood cells and neutropenia which indicates that you have a low number of neutrophils (immune cells that defend you from viruses and bacteria). It is possible that patients with additional medical conditions receive adjuvant chemotherapy (after surgery) as there is a lower risk of developing these side effects since other chemotherapy drugs are used11.
Chemotherapy after surgery
The adjuvant chemotherapy regimen recommended by the NHS includes both a taxane and an anthracycline drug11. Taxane chemotherapy drugs include paclitaxel (Taxol®), nab-paclitaxel (Abraxane®) and docetaxel (Taxotere®).
During the COVID19 pandemic, chemotherapy regimens have slightly changed. Some common intravenous chemotherapy drugs (e.g Taxol®) are being replaced by oral chemotherapy pills such as Capecitabine (Xeloda®), and Abraxane® might be prioritised over Taxol® due to its reduced toxicity (less side effects)17 (if you want understand the difference between Taxol and Abraxane, head to this Instagram post).
PARP (poly (ADP-ribose) polymerase) is a protein that helps both healthy and cancer cells repair DNA damage, allowing cells to survive and continue to function. PARP inhibitors work by blocking PARP proteins in cancer cells. This prevents them from repairing DNA damage, and often leads to cell death18.
PARP inhibitors are a therapy for those with BRCA genetic mutations, which are common among TNBC patients. This is because PARP inhibitors are able to cause the death of cells carrying these genetic mutations. Two of the main PARP inhibitors are Olaparib (Lynparza®) and Talazoparib (Talzenna®). Both therapies are currently being assessed by NICE for metastatic HER2-negative breast cancer patients carrying BRCA1/2 mutations after chemotherapy19,20. The publication of their decision has not yet been reported. Olaparib is only available in the UK under the Cancer Drug Fund for secondary ovarian cancer21.
The Cancer Drugs Fund is part of the British organisation that reviews new and existing drugs, called NICE. It was made to fund new drugs and accelerate the process of drugs becoming available in England. If there are recently developed treatments that may be of benefit to you, your specialist will fill out an application on your behalf. To find out more about Cancer Drugs Fund, head to Cancer Research UK’s website.
Immunotherapy uses the immune system to fight cancer. Therefore, it works by helping the immune system recognise and attack cancer cells. Some types of immunotherapy are also called targeted treatments or biological therapies.
Atezolizumab (Tecentriq®) with nab-paclitaxel (Abraxane®)
Atezolizumab is a monoclonal antibody and nab-paclitaxel is a chemotherapy drug. Atezolizumab blocks the protein PD-L1 which is responsible for preventing immune cells (mainly a type of immune cell called T-cell) attacking human cells. PD-L1 is located on the surface of some cancer cells and is recognised by a receptor (PD-1) on the surface of a type of immune cell (T-cell) (see figure 2 below).
Cancer cells trick the body into thinking they are normal cells by having PD-L1 proteins on their surface. If PD-L1 is blocked with atezolizumab, your immune cells detect cancer cells as foreign and harmful. Your body will then attack and kill these cancer cells22. Treatments can either block the protein on the cancer cell or the immune cell to stop the two from binding.
Secondary TNBC breast cancer tends to have earlier cancer recurrences that can often reach the lung and the brain. This therapy can increase overall survival by around 9.5 months of metastatic or locally inoperable TNBC patients that are PD-L1-positive15.
It is the first immunotherapy available at the NHS for untreated secondary or inoperable triple negative breast cancer23.
Pembrolizumab (Keytruda®) and Avelumab (Bavencio®)
“The interesting part is what does immunotherapy do on top of what we see with chemotherapy? […] The trial [combining chemotherapy plus immunotherapy before surgery] showed what we had hoped to see, in terms of increasing the number of patients responding to therapy, which is a very big step forward”– Dr. Peter Schmid, Queen Mary University of London; KEYNOTE-522 study.
Pembrolizumab blocks the action of the protein PD-1 and Avelumab blocks PD-L1. Both of them have shown promising results in clinical trials for people with advanced triple negative breast cancer that have previously been treated with chemotherapy24,25, and for those untreated in combination with chemotherapy 26. NICE may start to assess pembrolizumab in combination with neoadjuvant chemotherapy later this year27.
Research and future treatments
Research has shown that TNBC is not a single subtype. Recent studies are showing that triple-negative breast cancer can be divided into different groups depending on the molecules/proteins cells express. In fact, triple negative breast cancers are very heterogeneous and have diverse characteristics. For example, using gene analyses, some research groups have identified six different TNBC subtypes: two basal-like (BL1 and BL2), an immunomodulatory (IM), a mesenchymal (M), a mesenchymal stem–like (MSL), and a luminal androgen receptor (LAR) subtype 28 . These types of classifications are key for finding new therapeutic routes.
One of the most promising drugs currently undergoing a clinical trial for previously treated secondary TNBC is Sacituzumab Govitecan (Trodelvy®) which targets a new protein found in abundance in this type of cancer: TROP-2 29. This therapy is an antibody-drug conjugate which means that is a monoclonal antibody linked to a chemotherapy drug. The antibody is specific for TROP-2, and the chemotherapy drug is SN-38. The monoclonal antibody targets and binds to the cell and the chemotherapeutic becomes active, killing the cell. This therapy has been approved for use in TNBC in the US and is currently undergoing clinical trials in the UK measuring the survival benefit and could be on the UK market in the near future.
Common side effects
Chemotherapy targets all fast-dividing cells in your body. As cancer cells are fast-dividing, it is particularly these cells that are targeted and destroyed. But other fast-dividing cells are also affected, including hair follicles, the lining of the mouth, skin, nails and intestines. That’s why hair loss, brittle nails and diarrhoea are very common side-effects. Other very common side effects are sickness and vomiting.
Platinum-based chemotherapy may have severe side effects such as the risk of infection due to a drop in white blood cells (neutropenia), breathlessness and looking pale due to a drop in red blood cells (anaemia) and bruising (due to a drop of platelets in your blood). Other platinum side effects include fatigue, feeling sick, loss of appetite, diarrhoea, kidney damage, changes to your hearing and to the levels of minerals in your blood 30.
Anthracyclines’ side effects include vomiting, nausea and alopecia. However, it can also cause heart function problems. This is why you might have heart tests to check the health of your heart before and during chemotherapy31.
Some common side effects of Atezolizumab (Tecentriq®) are loss of appetite, difficulty breathing, fatigue, diarrhoea, feeling sick, skin changes, joint or back pain and urinary tract infections32. Lastly, the main side effects of PARP inhibitors are increased risk of infection, diarrhoea, feeling sick, indigestion, headaches and changes to how your kidney and/or liver works33.
Do you know that you can track your side effects with OWise? With over 30 side effects and symptoms to choose from, you can track any changes and share these with your care team and loved ones. Better communication with your care team can make sure you receive the best care possible.
And that’s all of the TNBC treatments summed up
We hope that you now better understand TNBC, the treatment options and that you can feel confident in discussions with your care team. Our aim is to make sure you are kept informed so make sure to follow our Instagram and Twitter accounts for any updates.
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