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 . 

Hi, I’ve been taking Anastrozole for 2.5 months + apart from the occasional hot flushes , i can’t say I’ve noticed anything else. As i have only finished 15 days of radiotherapy 9 days ago, im not sure if my low mood is because i am just grumpy, or the fact i am more tired than usual. What hasn’t helped me is that i have a severely osteoarthritic hip (bone on bone), which severtly limits my mobility, so i’m constantly in pain + tired! I can’t decide if I’m more tired than usual, but at the moment, i actually want to kill my husband!!!

I am new to the forum and am facing starting anastrozole. I am more frightened of the drug than I was throughout
lumpectomy, radiation, and 1 chemo treatment. Right now, I feel well and read about stroke, heart attacks, etc. as side effects from the hormone. I really am having a hard time getting started with it.

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I really think it is a personal choice. I was invasive DCIS and had two surgeries Dec 22 and Jan 23 and radiotherapy. I took Anastrazole against my real wishes for 6 weeks then had a 6 week break then stopped completely almost with the blessing of the team who said in my case it was of negligible benefit. Having read an awful lot of research papers and always been anti anything affecting hormones it wasn’t right for me and even the hospital said it was of negligible benefit in my case.

I made the choice to stop it after nearly 5 months but my cancer was a very slow growing one that rarely spreads . My Breast Consultant was also fine with this decision. My Oncologist had discharged me but I know she wouldn’t be pleased. I stopped because of joint pains / stiffness mainly but not everyone gets those and a lot of people take it without getting any significant problems . This is a safe place for us to discuss our problems and let out our frustrations but to anyone fairly new to this it may look like everyone is struggling with significant side effects - which isn’t true .

. The first few weeks I had lots of hot flushes and mood changes and a few other symptoms but all that settled down to an acceptable level . If you start it and this happens try not to be scared as it is your body adjusting to the drug and if you keep going drink plenty of water and exercise it should settle down after a while.

I didn’t discuss it as thoroughly as perhaps I should have done before stopping . There are options I have heard of that I wasn’t aware of at the time . The cancer I had may not reccur but I’m a good candidate for developing another one so I do sometimes wonder if I’ve done the right thing. I would advise you to discuss it with your BCN as you are worried. If there’s a breast cancer support group locally maybe talk to them about it as well.

Take care

I’ve just come off Anastrazole after 5 years. Stopped taking it 6 weeks ago. I was hoping the side effects would have subsided by now, but am feeling worse than ever, joint pain is worse, insomnia just as bad as ever. Can find very little helpful info on this - has anyone had similar experiences?

Interesting read and sorry to hear you have such unpleasant side effects. I’ve taken Letrozole prior to surgery to help shrink the tumour in my small breast, and after 6 months it did shrink it a bit so makes me feel safe. Then I was advised to stop taking letrozole during 4 and a half months of chemotherapy and have been back on Letrozole now for 6 months with a prescription for 7 years. For me Letrozole is a breeze compared the chemo. During chemo I did experience “chemo brain” in some of the days early after the infusions in each cycle, but no such brain fog/absent mindedness with Letrozole at all. As for muscle or joint pains the only ones I have are around the site of the mastectomy so I’m not attributing them to Letrozole. Being post menopausal, my main concern with AIs is the loss of bone over time, and I’ve been prescribed Ibandronic acid to prevent calcium from leaking out of my bones. I’m also hoping that yoga being weight bearing will help protect my bones too. As for the high cholesterol risk over time I’m watching my nutrition and trying to put in a fast walk now and then (not so easy when working at home). Endocrine treatment does protect the ones of us who have an ER+ breast cancer from recurrence, but I wonder if there is any worth talking to the oncologist about trying different AIs or even a different brand of Letrozole to see if the side effects are more bearable?

I am new to the forum even though I was diagnosed in 2019. I had two lumpectomies ( histology showed there was not a clear margin after the first. ) Large tumour removed-8cmx7cm thankfully no spread. 3 weeks of radiotherapy ended on Dec 10 2019. I have had six zoledronic infusions and take anastrozole daily.
I have experienced weight gain and joint pain which I am increasingly difficult to manage. I have now been on anastrozole for three years and 10 months and I am struggling with pain in my knees hips and finger joints. I am due to see my consultant next week and I’m wondering whether to suggest coming off anastrozole. I know that only I can make the decision but it feels like a difficult one for me. My oncologist recommended five years on anastrozole.
I realise I also have some memory issues and like other contributors I wondered whether this was age related-I am 77… my mother had dementia, and it is one of my fears.
I realised also that my psychological processing of having had breast cancer has been delayed as my husband of 52 years died suddenly a day after my radiotherapy ended. He had Parkinson’s disease and his high level of anxiety due to this meant that I played down my breast cancer and my anxiety about it. So I am delighted to find this forum

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Hi Stephp

So sorry to hear of the death of your husband when you were also going through so much with the BC.

My Dad also had Parkinsons and I did not tell him at all about the cancer due to his anxiety. I needed 3 ops to get rid of the blighter and excused myself from visits to his care home due to ‘having a cold’ / ‘stomach problem’ when I was having surgery .

I started on Anastrazole but the pain etc from the SE’s was very bad very quickly and my onc changed me to Exemestane, then Tamoxifen and finally Letrozole. So it is possible to try another one to see if it any better for you. For me each one came with a lesser version of the SEs of the previous one!

Another tip would be to try a different manufacturer of Anastrazole. I had ACCORD specified for my Letrozole as a change one month to SUN was horrendous.

I have now stopped the tablets (after 5 years) and yesterday realised that I don’t have any pain climbing the stairs, my hair is not falling out like it was and I can move my fingers better in the mornings. Sleeping better too. So hopefully all to the good.

best wishes