Stopping Anastrozole

Hello I am new to the forum. I was diagnosed with ER8 Stage 1 Breast Cancer in September 2023 with Negative Lymph nodes. I had a  lumpectomy followed by radiotherapy and I commenced Anastrozole in October 2023. Like everyone I have painful  wrist joints. But I have also been feeling very strange a kind of  dull brain, then over the last month what has shocked and frightened me  is I have began  to have problems with memory recall out of the blue when talking.  Not all of the time. There is no warning on the patient information  leaflet about cognitive impairment as a side effect.  So I have done some research and all the anti aromatase drugs effect the neuro- transmitters in the brain.  However despite the drug been taken by  thousands of women there is very little concrete research on what it does to our brains  if it effects some people more then others? and if the effects go after stopping the drug. A Cancer Group of Nurses in the USA have just started some research:  I have Reported the fact that we are not informed of this serious side effect  to the Medicines regulatory group  via the Yellow |Card system in the hope that it will stimulate further research.  If you are having  any Memory  problems since taking any of the anti oestrogen drugs Please can you report it too.

In the mean time  my fear of loosing brain function has caused me to stop taking the drug  I am waiting an appointment with my oncologist.  I read this known side effect usually started after 12 - 18 months after starting the drug but mine is much earlier. I  also worry  that as I am small the one dose that is supposed to treat all!  is too large for me?  It is a frightening decision to stop taken the drug.

Let me know your thoughts and experiences please. Oh I forgot say I’m 66 years old.

Please speak to your oncologist before making decisions. They really do know the territory. Not a good idea to stop the AIs been taking 4 years no problem at all with brain function 

Hi @Lakesiderunner   I assume that you had your treatment in 2022 not 2023 as written and if so, you and I are very similar.  I had ER8/8 S1 G1 IDC, surgery in Sept 22, rads in Nov 22 and started Letrozole at the end of October 22.  I was 66, now 67.

I haven’t experienced any joint pain which is so typical on endocrine treatment but I immediately suffered from vaginal atrophy (currently under control) and cognitive issues.  Memory problems, language problems, low mood, brain fog and fatigue, it has been extremely distressing.  There is a high incidence of dementia in my family, indeed I was my mother’s principal carer for three years, and the thought of living with and dying from that appalling disease frightens me considerably more than dying from breast cancer so I discussed it with a neurologist six weeks ago and with the head oncologist in my HA, two weeks ago telling them both exactly what I have just said here, that I will take all steps available to me to prevent the onset of dementia including opening myself up to a BC recurrence by stopping the AI if the cognitive decline continues.  Neither was shocked or dismissive about my stance but both said that there is no evidence that AIs or the eradication of oestrogen cause cognitive decline.  Both conceded, however, that there has been no major long-term study in to that connection.   Alas a randomised, double blind, controlled study would take at least two decades to complete so, even if one was started now, it would be too late for the results to influence  our treatment plan.  I have to say, my oncologist immediately said she is fascinated by the topic, particularly as she is a peri menopausal woman, but she deals in known facts not conjecture so recommends I keep taking the Letrozole for the time being.  HOWEVER she did agree to give me a 6 week break, which I have just finished, and the good news is a lot of the symptoms have cleared although my memory isn’t quite back to its original level but stress and anxiety about it all might be playing a part in that.  I have just started taking Letrozole again and I expect the symptoms will occur again but we shall see.  

Ultimately no-one can force you to take the drug - some women elect not to take it and others choose to stop taking it after a given period - but it is a massive gamble.  Stopping it in the short term until you get to speak to your oncologist isn’t going to harm you but expect significant push-back from him/her when you get to discuss it as their focus is on eliminating cancer not on taking a holistic approach.  I have skin in this particular game so can you let me know how you get on? 

I am 67 and I am taking letrozole, have done now since around October last year. NB that was 2022, so I think you started taking Anastrozole about the same time. Not in 2023…

i have found my memory declining a lot, which may be due to age or to letrozole or both!

I certainly find myself forgetting all sorts of useful information e.g. today I was meant to pick up a packet of letrozole from my GP surgery at 4 pm. At 5.50 pm I remembered so had to rush off in the car to collect it. But it wasn’t ready!

So the pharmacist was possibly as forgetful as me.

I had to take the prescription away as I run out on Monday next week, Bank Holidays are a great nuisance. As is having to remember a lot more about what medicines to take and when. I found it a lot easier when I took the occasional aspirin, or paracetamol. Now I am chronically ill.


I am so glad to have found this forum. I have been on Anastrozole for 2.5 years now. I thought I was losing my mind. The aches, the teeth issues, the extreme hair thinning, the memory fumbles and osteopenia is sending me into a state if depression. I stopped taking Anastrozole a week ago. My oncologist has now prescribed Letrozole which I have to wait 5 weeks before starting. However, I see that  Letrozole has the same side effects. Does anyone know of something out there with less affects?

I don’t have any of those side effects so don’t assume you will .