Breast cancer is the second most common cancer people face all over the world. In the United States, 13% of women¹ will develop invasive breast cancer at some point in their lifetime. While numerous types of breast cancer exist, not all of them require similar treatment.
HER2 breast cancer deserves special attention. While more aggressive than other breast cancers, it's also highly treatable. When diagnosed early, the survival rate can be impressive. This abnormality can cause breast cancer in both men and women.
Learning all you can about this type of breast cancer can help you make the right decision about timely testing and the course of treatment.
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HER2 stands for human epidermal growth factor receptor 2. This gene is responsible for helping cells grow, divide, and repair themselves. However, in about 10% to 20% of breast cancers, the HER2 gene "breaks" and starts making extra copies of itself.
These copies order breast cells to make too many HER2 receptors or increase their activity, which in turn causes cancer cells to multiply.
HER2 breast cancer is cancer that has a HER2 gene defect. These defects may develop at any point in a person's life. As of today, researchers don't know what causes the gene to start acting abnormally.
While HER2 breast cancer is more aggressive than other cancers and has a higher tendency to metastasize to the brain, targeted treatments demonstrate excellent results. This is why if you've been diagnosed with breast cancer, it's imperative to test for the HER2 gene abnormality.
When cancer recurs or spreads, it needs to be retested for the HER2 gene deformity. Research has shown that HER2 positive cancers can turn into HER2 negative cancers over time.
HER2 positive vs. HER2 negative
Since up to 20% of breast cancers test positive for HER2 gene deformity, it's important to identify whether a patient has this abnormality as early as possible.
When the tests find the broken HER2 gene in breast cancer cells, the cancer is defined as HER2 positive. In cases where cancer doesn't have abnormal HER2 proteins, it is HER2 negative.
The HER2 status of breast cancer affects the course of treatment.
The symptoms of HER2 breast cancer are unfortunately similar to all types of breast cancers. It's impossible to diagnose HER2 breast cancer by symptoms alone.
The common signs of breast cancer include:
Lumps in the breast
Excessive breast swelling and tenderness
Irritated, red, or dimpled breast skin
A change in the breast's shape
Pain in the breast or nipple
Many women discover breast cancer during self-exams, routine ultrasounds, or mammograms.
To diagnose a patient with HER2 breast cancer, the doctor will take a sample of the tumor tissue for further evaluation. It can be done through:
Fine-needle aspiration biopsy – a tiny sample of breast cells or fluid is removed with a thin needle.
Core needle biopsy - a tiny sample of breast cells or fluid is removed with a larger needle.
Surgical biopsy – a doctor removes a sample through a small cut.
The type of biopsy depends on several factors, including the location and size of the tumor.
The two tests that can determine whether breast cancer is HER2 positive are:
Immunohistochemistry (IHC) – measures the amount of HER2 proteins on the cell's surface by using a chemical dye stain. The amount of observed staining reflects the quantity of HER2 protein. If the score is 3+, the cancer is HER2 positive.
Fluorescence In Situ Hybridization (FISH) –uses chemicals that attach themselves to HER2 proteins and glow in the dark.
A certain controversy surrounds IHC testing since this method can provide false-negative results. This, in turn, could lead to the wrong course of treatment.
The FISH test is more expensive and time-consuming than IHC testing because it requires a certified pathologist to perform it, a fluorescent microscope, and a special darkroom. That's why many clinics prefer to start with an IHC test. If the results are controversial, doctors may order the FISH test.
Unfortunately, according to Jeffrey S. Ross, MD², about 3% to 4% of all IHC tests in the U.S. generate false-negative results that are never followed by a FISH test.
An oncologist will most likely recommend HER2 testing if:
A person has a newly diagnosed invasive breast cancer.
A person is diagnosed with metastatic breast cancer.
A person has recurrent breast cancer (cancer that comes back after successful treatment).
A person who subsequently develops metastatic disease (spread beyond the breast tissue) should have that new area of disease retested.
Once the results are in, the doctor adjusts the course of treatment to target the HER2-positive breast cancer.
The treatment of HER2 breast cancer is different from other breast cancer treatments. In addition to standard protocol, doctors recommend HER2-specific options that have an impressive success rate when battling HER2 proteins.
Often these medications will be used prior to any surgical removal of the main area of cancer “neoadjuvant,” as well as post any surgical treatments to try and ensure any potentially missed cells are removed - “adjuvant” therapy.
General breast cancer therapy involves a combination of surgery, chemotherapy, and potentially radiotherapy. The aim is to eliminate all detectable cancer cells and prevent a recurrence.
HER2 breast cancers may also have hormone receptors that can be targeted with hormonal therapies.
Monoclonal antibodies are lab-made proteins that attach themselves to cancer cells. They can flag cancer cells, so the body's immune system finds and destroys them. These proteins can also carry harmful substances (drugs, toxins, and radioactive substances) to cancer cells.
Trastuzumab (Herceptin) – this drug can be effective for early and advanced HER2-positive breast cancer. It's administered intravenously or through subcutaneous injection.
Pertuzumab (Perjeta) – this drug is used in combination with Trastuzumab for early-stage and metastatic HER2 breast cancer.
Margetuximab (Margenza) - this drug is used in combination with chemotherapy for early-stage and advanced HER2 breast cancer.
Depending on the situation, monoclonal antibodies can be used alone or in combination with other treatments.
Antibody-drug conjugates (ADC)
This biological drug is created by attaching an anticancer molecule drug (chemotherapy drug) to a monoclonal antibody. The antibody, in turn, finds HER2 cancer cells, attaches itself to them, and brings the chemotherapy drug straight to the target.
HER2 is a kinase protein. Kinases add chemicals called phosphates to other molecules in the cells. Their strong activity could cause cancer cells to grow.
Kinase inhibitors block the action of HER2 proteins. Neratinib, lapatinib, tucatinib, and Pyrotinib are tyrosine kinase inhibitors that can help treat HER2 breast cancer. They are administered in pill form.
Targeted HER2 breast cancer therapy can have serious side effects, including:
Congestive heart failure
GI tract disorders
If you experience any of the above issues during therapy, an oncologist will adjust your treatment accordingly.
Is HER2 breast cancer curable?
Targeted therapies make HER2-positive breast cancer highly curable, especially when diagnosed early. Oncologists prefer to use aggressive therapies to defeat HER2 breast cancer in its early stages.
Researchers are yet to find the cause of HER2 breast cancer. The only thing they know for sure is that HER2 breast cancer isn't hereditary. You can't inherit the mutated HER2 gene from a parent.
Possible factors for HER2 breast cancer include:
Age - HER2 breast cancer tends to affect younger women
Hormone replacement therapy (HRT) use - HER2 is less likely in patients previously on HRT
Alcohol consumption - HER2 positive breast cancer patients are less likely to have used alcohol
Ethnicity – Asian and Hispanic individuals have a higher risk of being diagnosed with HER2 breast cancer.
It's still not clear what causes the HER2 gene to break. However, making appropriate lifestyle changes and participating in regular screening can ensure cancers are detected early.
Since HER2 breast cancer responds well to targeted treatment, the survival rate is fairly high. The four-year survival rate varies from 82.7% to 90.3%³.
The risk of recurrence for HER2 breast cancer in the years five to ten is low. According to a study⁴, patients without lymph node involvement had a recurrence rate of 3.23%. For patients with lymph node involvement, the rate was 6.39%.
While aggressive, HER2 breast cancers respond well to targeted therapy; the four-year survival rate exceeds 90%. Since causes are still unknown, oncologists recommend testing all breast cancer patients for the presence of the abnormal HER2 gene.
By diagnosing HER2-positive breast cancer early, it's possible to adjust the treatment accordingly and achieve a cure.