Knowing your ESR1 status provides your care team with invaluable insights that can help optimize your treatment outcomes. To help facilitate conversations with your care team surrounding ESR1 mutations and testing, we’ve transcribed a few key points from our discussion with Dr. Anne O’Dea.
Dr. O’Dea is the Medical Director of Breast Cancer Survivorship and Breast Cancer Clinical Research Program Services at the University of Kansas Medical Center with extensive experience in breast cancer research.
If you or a loved one has been diagnosed with breast cancer, we hope the following information encourages you to speak to your care team to uncover your ESR1 status.
The following questions and responses have been lightly edited for grammatical purposes.
Q: What is an ESR1 mutation in breast cancer?
A: ESR1 is a very important genomic alteration that happens in some hormone-positive breast cancer cells, especially in advanced or metastatic breast cancer.
First, let’s talk a little bit about what a mutation is. Over time, metastatic breast cancer cells can change or mutate. They can develop acquired resistance mechanisms under the pressure of treatment. Mutations may make advanced or metastatic breast cancer difficult to treat.
Commonly at the initial treatments for hormone-positive, HER2-negative metastatic breast cancer, most patients will receive a hormonal therapy or an endocrine therapy, either with or without an inhibitor for their first-line treatment. This is really the standard of care within our country. The usual time on treatment is about a year or more although there is a variability of how cancers will respond to that first-line treatment.
After the initial success, a lot of patients will need a change in treatment. Unfortunately, this is something that we see in advanced breast cancer. As the treatment goes on, the cancer cells become smarter. They develop mutations which are acquired ways to become resistant to cancer therapy.
It’s very similar to if we have an infection, for example, bronchitis. Our primary care doctor puts us on the same antibiotic over and over again and although initially that antibiotic may have worked very well, it starts working less well because the infection is becoming smarter and developing resistance. Cancer cells can behave in very much the same way.
It’s important to understand that these mutations are very common, especially ESR1 mutations in hormone-positive, HER2-negative metastatic breast cancer. Almost 50% of people that have hormone-positive, HER2-negative metastatic breast cancer may develop an ESR1 mutation after progression on hormone therapy. There’s also some evidence that has been well-published that a mutation may allow cancer to progress or spread more quickly, so it might encourage the cancer’s ability to metastasize to other places of the body.
It’s important to understand that these mutations can happen over time. Just because you’re a patient who has had your cancer tested initially doesn’t mean a mutation won’t develop over time under the pressure of treatment.
Q: Why is it important to get tested for an ESR1 mutation?
A: We know that mutations can cause resistance to certain hormone therapies because for example, it might cause a change in the binding site where that particular drug might bind. So if the drug can’t bind, it can’t impact the cancer cell the way it’s supposed to. For some patients, an ESR1 mutation may be the reason why the cancer is progressing.
It’s important to know why your current treatment may have stopped working so you know which treatment options may be available for you. This is something we want to do every time patients who have hormone-positive, HER2-negative advanced breast cancer have a change in their cancer or progression in their cancer. We want to make sure we get this information because we want to be treating the most recent or the most current representation of the cancer, understanding that cancer is always changing over time.
If your cancer has developed a mutation, the results may show why your disease may have progressed which gives us some insight into why that is happening with the cancer.
Q: How can you get tested for an ESR1 mutation?
A: Mutations are detected through a blood test and it’s very accurate. We get the results back in about a week. Typically when I talk to a patient about this, I may be hearing about new symptoms and have an instinct that the patient’s cancer might be starting to change, evolve, or become more active. In that visit, I might ask if he or she would be willing to have an extra tube of blood obtained so that we can test for an ESR1 mutation.
I always like to explain to patients that doing this blood test allows us to gain an understanding. For example, if they have a tumor in their lung and their liver, each of those tumors might be a little bit different. If we choose to do a biopsy of one of those tumors, we’re going to get the information back about the genetic makeup of that specific tumor that we biopsied. It may not be exactly representative of all the tumors. Some of the other tumors may have different mutations
When we do a blood test, it allows us to account for all of the different types of tumors which are circulating DNA into the bloodstream. So I find the mutation blood test to be particularly helpful and informative when patients have more than one tumor, or especially when they have tumors and locations that are difficult to biopsy. This can be done at your doctor’s office or any lab.
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