Treating HER2 Breast Cancers
- A new recommendation in the UK gives more people with unresectable (not removable with surgery), metastatic (stage four) HER2-positive breast cancer access to the breakthrough cancer therapy called Enhertu.
- Enhertu is a specifically engineered HER2-directed antibody drug. Right now, it can be used in patients with HER2-positive and HER2-low metastatic breast cancer (having metastatic cancer means it has spread beyond its place of origin).
- You should ask your doctor for your HER2 score. If it's unknown, ask if you need another biopsy to determine the true nature of your breast cancer, and then ask if Enhertu is a drug you're eligible to receive.
Hundreds of more people are now eligible to receive the cancer therapy Enhertu after the UK’s National Institute for Health and Care Excellence just recommended the drug for patients with unresectable (not removable with surgery), metastatic (stage four) HER2-positive breast cancer after at least one anti-HER2 therapy.
Read MoreWhat Is Enhertu?
Enhertu is targeted therapy approach called an antibody-drug conjugate, or ADC. That means that Enhertu is made up of a monoclonal antibody chemically linked to a drug. The monoclonal antibody portion of an antibody-drug conjugate binds to specific proteins or receptors found on certain types of cells (including cancer cells) and then the linked drug enters the cells and kills them without harming other cells.
Trastuzumab is the antibody for Enhertu and durexecan is the payload, or chemo. So trastuzumab binds onto whatever HER2 proteins it can find on cancer cells and then durexecan prevents the cells’ DNA from replicating.
Right now, Enhertu can be used in patients with HER2-positive and HER2-low metastatic breast cancer (having metastatic cancer means it has spread beyond its place of origin).
HER2 and Breast Cancer
HER2, in general, is a protein that helps breast cancer cells grow quickly (HER2 is an acronym for Human Epidermal Growth Factor 2).
"We have entered the era of precision medicine," Dr. Yuan Yuan, Director of Breast Medical Oncology at Cedars-Sinai, previously told SurvivorNet. "I think that's encouraging. This is more applied to the metastatic setting. Now we're able to look at one's genomic profile.
“HER2 is scratching the surface.”
The Unique Features of Breast Cancer: Deciding the Right Course of Treatment
The presence of HER2 in breast cancers has traditionally been divided into two groups, either positive or negative. But that organization left about 50% of patients somewhere in the middle. So, now researchers are looking into an additional classification called HER2 "low."
Breast cancer cells with higher than normal levels of HER2 are called HER2-positive. These cells are found in about 15% to 20% of all breast tumors. These cancers tend to grow and spread faster than breast cancers that are HER2-negative, but they are also much more likely to respond to treatment with drugs that target the HER2 protein, like Enhertu.
HER2-low cancers have a minimal amount of HER2 expression but do not meet the classic definition for HER2-positive tumors. This newer grouping is very important as it represents approximately 50 percent of all patients with breast cancer and we’ve seen patients in this grouping respond to Enhertu.
"What we've learned is that some of these patients we thought were HER2 negative are actually HER2 low,” SurvivorNet advisor Dr. Elizabeth Comen, a medical oncologist at Memorial Sloan Kettering Cancer Center, told SurvivorNet.
Do You Know Your HER2 Score?
Even though we know antibody-drug conjugates like Enhertu can function with low levels of HER2 expression, the minimum level of HER2 required for them to benefit patients is not known at this time.
Still, it is important that breast cancer patients ask their doctors about their HER2 score to see if they qualify for targeted therapies like Enhertu. During an interview on ABC's “Good Morning America,” Dr. Comen spoke about the excitement of Enhertu and this new classification for metastatic breast cancer patients.
"One of the most challenging types of cancer to treat is metastatic breast cancer," Dr. Comen said. "And a new treatment, an FDA approved treatment, called Enhertu or T-DXd is being used to improve the survival of patients with a new classification of metastatic breast cancer called HER2-low metastatic breast cancer.
“So, for anybody watching, if they or their loved one has metastatic breast cancer, it's critical that they ask their doctor, 'Do I have HER2-low breast cancer and might this be an appropriate treatment for me?"
Contributing: Dr. Rodrigo Leão Edelmuth
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