ESR1 mutations are rarely present at diagnosis of hormone receptor-positive breast cancer but emerge under the selective pressure of aromatase inhibitors. A test done on the original tumour, or at an earlier progression, can therefore miss a mutation that is present now.
Circulating tumour DNA from a blood sample is the practical way to detect it at progression, and the result now directs a choice between therapies that target the mutation and those that do not.
- Test for ESR1 mutation at each progression on endocrine therapy, not only once.
- Use circulating tumour DNA from blood, which captures newly acquired mutations.
- Do not rely on an ESR1 result from the primary tumour to guide later-line treatment.
- Repeat testing if a previous blood test was negative and the disease has progressed again.
Why it matters
The mutation is acquired during treatment, so an old negative result can mislead.
Read the rest in the app
You have read your two free briefings this month. The app carries all 27 specialties, every morning, free — and this finding is waiting in it.
Scan to keep reading on your phone. No account needed to start.
Tomorrow morning, before your first patient
One edition a day for oncology, written by the desk, every claim tied to its paper. Six minutes.
Get the app — free