ESR1 FAQs

ESR1 FAQs

What are ESR1 mutations?
ESR1 mutations are changes in the ESR1 gene that may diminish the effects of, or stop endocrine therapies from working (resistance mutations). ESR1 mutations develop after taking certain endocrine therapies (ET). The more ET received, the higher the chance of developing an ESR1 mutation.

Are ESR1 mutations common?
ESR1 mutations are common – they may be found in ~40% of patients who received prior ET.

Are ESR1 mutations hereditary?
ESR1 mutations are somatic mutations, which means they can occur in any of the cells of the body. However, they are not inherited (known as germline mutations) and are therefore not passed on to children.

How do ESR1 mutations impact cancer treatment?
ESR1 mutations may make endocrine therapy less effective or stop working, causing the tumor to resulting in tumor/disease progression. Knowing the a/mBC biomarker mutation status for genes such as ESR1, PIK3CA, PTEN and others, may inform clinical decision making by helping the healthcare team decide which treatment options are more appropriate for patients.

How can a person know if they have an ESR1 mutation?
The ESR1 mutation status can be determined through what is known as an ESR1 mutation test. ESR1 mutations can be detected by a blood test, also called a liquid biopsy. Current guidelines recommend ESR1 testing at each disease progression using either a blood test, or a fresh tissue biopsy.

When are ESR1 mutations most likely to be found?
It is important to test for an ESR1 mutation every time the cancer progresses. Breast cancer in people with ER+/HER2- a/mBC may eventually get worse while on ET. This is called disease progression and may happen when ET is not working well enough.

What is a liquid biopsy?
A liquid biopsy is a technique that uses a blood sample to detect, for example, ESR1 mutations. DNA is extracted from the blood sample and analyzed in a lab. A liquid biopsy is minimally invasive, samples can be collected fast, and is easy to perform at each progression.

Is it good or bad to have a positive ESR1 mutation test?
Knowing a person’s ESR1 status is neither good or bad but it will help the healthcare team decide which treatment options are most appropriate. If a person’s metastatic breast cancer has an ESR1 mutation, it may require a different treatment.

Is one ESR1 test enough?
Metastatic breast cancer changes over time and throughout treatment. As ESR1 mutations emerge due to ET, a test for ESR1 mutations should be performed at each progression if not detected previously.

How long does an ESR1 test take?
Typically, the report for an ESR1 test with liquid biopsy is shared with the healthcare team within 14 days. However, some analysis labs might have different timelines.