ESR1 Mutation Her2 negative + hormones, bone mets


My Mum was diagnosed with a primary in April 2020- surgery went well, no chemo just radio and anastrozole & bone tablet’s since June.

Scans in May & June before she started medication showed arthritis but no evidence of mets.  Routine scan at end of August approx 3 months into Anastrozole showed subtle but extensive bone mets/infiltration changes in spine.

No major symptoms, if any. Blood tests were ok apart from tumour markers which they said is useful to track progression or if treatment is working.

Oncologist recommends keeping her on first line treatment and monitoring blood tests and a further ct scan next week.

But he mentions in a letter a possible ESR1 mutation which means he will have to move her onto a second line treatment of injections and cdk inhibitor If this is the case. 

Has anyone else had similar, or can explain what an ESR1 mutation is? Assuming its a change of sorts from the primary tumour which was removed. 

Thank you!


Sorry to hear about your Mum, it’s always feels quite devastating to all when you get a secondary BC diagnosis. However, over time, most of us have learnt to live with it so I’m hoping your Mum will too.

As to your question about the mutation I’ve not heard of it on here so you may not get any responses. If it’s something your Mums oncologist has said it would be worth asking them the next time you see them to see how this might affect your Mums treatment. Someone else on the forum might have heard of it and be able to point you in the right direction though.

Good luck with the scan and that should show whether the current treatment is being effective.


Hi Danny2020,

My mum is also being tested for this ESR1 mutation and I wondered how your mum was getting on? Did your mum end up having the mutation and what was the next line of treatment? 

There is no information in the search bar on this ESR1. Nicky was well informed on all things breast cancer and it seems even Nicky couldn’t shine a light on the topic. 

I hope your mum is doing well xxx