It’s All About HER2-Positive Breast Cancer

Woman holding a magnifying glass

We’re kicking off our in-depth explorations of breast cancer subtypes with early HER2-positive breast cancer. 20-25% of breast cancers have high levels of HER2 protein1, which can influence outlook and treatment. Here we are going to explain exactly what HER2 is and how it can affect your treatment plan.

So, what is HER2?

Human Epidermal Growth Factor Receptor 2, commonly known as HER2, is a protein on the surface of cells and acts as a receptor, responding to signals from its environment. Normally HER2 is responsible for the healthy growth and development of cells. However, when the HER2 protein is present in high amounts (overexpressed) on the cell surface of breast cancer cells this leads to abnormal cell division and growth. 

HER2 Receptors on cancer cells

How do I know if I’m HER2-positive or negative? 

The analysis of your tissue sample from a biopsy or surgery indicates if your tumour over expresses the HER2 protein. The expression of this protein is analysed by a staining technique called immunohistochemistry (IHC). If the IHC result is 0 or 1+, your sample is considered HER2-negative. If it is 3+ it is HER2-positive and if it is 2+ the result is inconclusive 2. You can review this in your pathology report. To find out more about the contents of your pathology report, head to our previous blog.   

Are there treatments specific for HER2-positive breast cancer? 

The significance of HER2 in the growth of breast cancer cells drove research for treatments that targeted the protein. This was first achieved by the organisation Genentech, who in the 1990’s developed Trastuzumab, commercially known as Herceptin®. Herceptin® is now the standard treatment for early and advanced HER2-positive breast cancer. However, the further discovery for treatments continued. Particularly in the last decade, we have seen a rise in the number of HER2 targeted therapies coming to the market. 

Did you know?

The future of Herceptin® was almost halted by the disbanding of cancer drug development in Genentech. However in the late 1980’s, the mother of a senior Genentech vice president was diagnosed with breast cancer. “Just like that, one man flipped the switch on HER2.” He convinced his colleagues that Herceptin® was worth Genentech’s investment. 

Robert Bazell, The Making of Herceptin®, a Revolutionary Treatment for Breast Cancer

Whilst this is invaluable for people to get the best care possible, with all the different terminology and decisions to be made, it can be easy to feel overwhelmed. So we have pulled together all the different HER2 treatment options you could have on the NHS. These are classified into three types: Monoclonal antibodies, antibody-drug conjugates and kinase inhibitors. In this blog, we are going to identify them all and explain how they work.

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 may differ to those in England 3.

Did you know you can add all your treatments into OWise, creating one easy-to-view treatment plan? The app also includes 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. 


1. Monoclonal antibodies

Monoclonal antibodies are drugs that block the HER2 receptor, blocking the pathway of HER2 and reducing the cell growth. To find out more on Monoclonal Antibodies, head to our previous blog. Trastuzumab and Pertuzumab are the most common monoclonal antibody therapies, which we will explore further here. 

1.1 Trastuzumab (Herceptin®)

This first targeted therapy for HER2 is given intravenously for both early and advanced breast cancer, often alongside chemotherapy before or after surgery.

Herceptin® was the original brand name for the drug, however several similar versions (called biosimilars) are now available. Biosimilars for Herceptin® include Ogivri®, Herzuma®, Ontruzant®, Trazimera®, and Kanjinti®. They are clinically identical, with no changes in effectiveness. However, having multiple options on the drug market allows for the driving down of costs. Although practically identical in their treatment against cancer, they should not be used interchangeably and therefore you are commonly prescribed the brand name rather than the generic name6.

Did you know?

Herceptin® was a breakthrough for HER2-positive breast cancer subtypes. Clinical trials showed that the introduction of Herceptin® halved cancer recurrence and reduced mortality by 30%7,8,9. To find out more about the history of Herceptin®, check out our blog

1.2 Pertuzumab (Perjeta®)
Herceptin working with HER2 Receptors

Pertuzumab, another HER2-specific monoclonal antibody, can be used for both primary and secondary breast cancer. It is included in standard care for neoadjuvant (before surgery) treatment in early breast cancer, alongside trastuzumab and chemotherapy. This is offered to people with locally advanced, inflammatory or early-stage breast cancer at high risk of recurrence12

In the study that supported NICE’s decision to give pertuzumab as adjuvant (after surgery) therapy for early breast cancer, it was found that adding pertuzumab to standard trastuzumab and chemotherapy increased disease-free survival13. This means that after treatment, there was a decreased likelihood of breast cancer spreading to other parts of the body. This did not include the appearance of other types of cancer. This is offered to people with lymph node positive early breast cancer (N1 and higher in TNM staging), as the cancer is more likely to recur in this group.

Pertuzumab is also offered alongside trastuzumab and docetaxel for locally recurrent breast cancer in adults who have not had previous anti-HER2 therapy or chemotherapy and are unable to have surgery to remove the cancer. This was after a review in 2018 that found pertuzumab significantly improved progression-free and overall survival14.

1.3 Trastuzumab-hyaluronidase (PHESGO®) injection

In April 2021, an injection called PHESGO®️ was offered by the NHS for people with HER2 positive breast cancer. PHESGO®️ contains both pertuzumab with trastuzumab which were previously given as separate IV infusions. It also includes hyaluronidase protein which helps metabolise these targeted drugs so they can be administered together in one 5 min injection under the skin on your thigh. This significantly cuts treatment time.

Whether administration via injection or IV infusion would be suitable depends on whether the patient can receive treatments at home, the local support that is available and whether other IV infused treatments are included in their treatment plan. If they are receiving other IV treatments, having the injection at home would not save a significant time in hospital, one of the main benefits of the PHESGO injection11

2. Antibody drug conjugates

An antibody-drug conjugate (ADC) is a monoclonal antibody linked to a chemotherapy drug. The monoclonal antibody targets and binds to the cell. The chemotherapeutic agent then becomes active when it enters the cell. This means that HER2-positive breast cancer cells can be targeted, and the cytotoxic effects of chemotherapy concentrated to the cancer cells. 

Diagram explaining antibody conjugates

2.1 Ado-trastuzumab emtansine (Kadcyla® or TDM-1)

Kadcyla® is an intravenous drug made up of trastuzumab and the chemotherapy drug emtansine. Kadcyla® is approved by NICE to be given for early breast cancer in the NHS. Clinical trial evidence showed that the use of Kadcyla increases the time people remain free of disease compared to trastuzumab alone16.

“Additional treatment options that can increase the amount of time in which people remain free of disease after surgery, and perhaps stop it from coming back altogether, are particularly welcome.  We are therefore pleased to be able to recommend that trastuzumab emtansine is made available routinely for people with HER2-positive early breast cancer after surgery.”

Meindert Boysen, deputy chief executive and director of the Centre for Health Technology Evaluation at NICE

Kadcyla® can be recommended to people with early HER2+ breast cancer who still have cancer remaining after receiving treatment before surgery. Trastuzumab emtansine can also be a treatment option for HER2+ breast cancer that is locally recurrent or cannot be operated on and has been previously treated with trastuzumab and taxane chemotherapy. The patient must have been previously treated for locally advanced cancer or developed a recurrence within 6 months of finishing treatment after surgery17

3. Kinase inhibitors

HER2 is a type of protein known as a kinase. Kinases are proteins in cells that receive signals to prompt the cell to grow, divide or die. Therapies that block kinases are called kinase inhibitors. Whilst monoclonal antibodies block the HER2 receptor by binding to it outside the cell, kinase inhibitors block the pathway within the cell. This means that if they receive a signal that the cell should divide or grow, the protein cannot carry it out.

Kinase Inhibitors working with HER2 receptors

3.1 Neratinib

Neratinib (Nerlynx®) are oral pills used in HER2+ and Hormone Receptor-positive, early-stage breast cancer. They can be given if there are still cancer cells remaining after neoadjuvant (before surgery) chemotherapy. The treatment is given after the adjuvant (after surgery) trastuzumab (sometimes called Herceptin®) treatment, which should have completed less than a year ago21

What side effects will I be at risk of?

There are some common side effects for all HER2 therapies, however each drug varies in specific side effects that you may be at high risk of. There are some excellent resources online that give you a breakdown of the top side effects, such as Cancer Research UK’s A-Z list of cancer drugs.

It is well known that cardiac toxicity (heart dysfunction) is one of the most common adverse effects among patients receiving chemotherapy and HER2-directed therapy such as trastuzumab, pertuzumab or TDM-1. Therefore people receiving trastuzumab typically undergo cardiac monitoring, and treatment should be stopped if a heart measure called left ventricular ejection fraction (LEVF) drops by 10% from baseline and to below 50%25. However, what is less clear are the long-term cardiac complications for breast cancer survivors who received such therapy in the past26.  Recent studies have suggested that exercise training such as high intensity training could help prevent cardiac toxicity after cancer treatment27

Other common side effects you may experience are28:

  • Sleep problems
  • Muscle/joint pain
  • Redness at the IV site
  • Diarrhoea
  • Nausea
  • Tiredness
  • Headache
  • Mouth sores
  • Loss of appetite
  • Cold symptoms
  • Rash

Neratinib and the combination of pertuzumab with trastuzumab can cause severe diarrhoea, so it is crucial to let your health team know any changes in bowel habits as they happen. 

Some kinase inhibitors, including neratinib, can cause liver problems. Regular blood tests will be taken to check your liver function, but watch out for itchy or yellowing of the skin, dark urine or pain in the right upper belly area29

And that’s HER2-positive treatment summed up

We hope that you now better understand your treatment options and can feel confident in discussions with your care team. Whilst we have included early HER2-positive treatment currently available on the NHS, there are currently clinical trials being run and new treatments may become available in the near future. We want to make sure you are kept informed so make sure to follow our Instagram and Twitter for any updates. 

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