Changing from Tamoxifen to an Aromatase inhibitor

Hi, I had a wide local excision for grade 2 breast cancer + IG DCIS. ER/PR positive, HER2 negative. I then had radiotherapy with BOOST and have now been on tamoxifen for 3 1/2 years. I have recently had a hormone test which has shown that I’m now post menopausal so the advice has been for me to change to an Aromatase inhibitor for the remaining 1 1/2 years. I’ve read the literature and spoken to my breast care nurse but I’m really not sure whether to change or not. I’ve had to have endometrial polyps removed 3 times since taking tamoxifen (I was told the polyps were tamoxifen induced) and I have had flushing and sweats since I started and memory/brain fog has been quite noticeable (although I wonder whether this could have been partly an effect of being peri menopausal). However I know that once I stop tamoxifen these symptoms will stop. I’m really worried about taking AI’s because of the chance of osteoporosis and joint pains which wouldn’t be reversible and also hair loss seems to be more likely. My BC nurse said that AI’s give about a 2% better protection than tamoxifen so although the side effects have been pretty awful on tamoxifen I wonder whether I would be better to stick with the devil I know for such a small, benefit! Also I did ask if I could go back to tamoxifen if I experienced these side effects but she wasn’t too keen for me to do that. I have exercised regularly and am very active which I have found has really helped my mood and getting through my treatment. It would have a very negative effect on my mental health if I could not exercise due to pain. I know only I can make the decision but I’m just hoping for some guidance/advice that might help me make the decision. Thank you. 

Hello Dorsetdumplin

Thank you for your post.

It is natural to worry about a change in breast cancer treatment. It is understandable you are wondering whether it would be best for you to stay on tamoxifen as you are familiar with how you feel on the drug, or whether to switch to letrozole which you are not familiar with. The uncertainty of side effects and how a new drug may impact on your physical and mental wellbeing can cause a lot of anxiety and worry.

Like any drug, letrozole can cause side effect however everyone reacts differently to drugs and some people have more side effects than others. It is difficult to say how you may find a change in treatment. It is good to hear you have talked this through with your breast care nurse and what benefit of changing treatment is to you.

It’s good to see you have remained physically active and we know this has a range of health benefits. It might be worth asking your breast care nurse again about going back onto tamoxifen if you did experience side effects like joint pain with letrozole that could stop you exercising.

You mentioned that you are worried about osteoporosis so do talk this through with your breast care nurse or specialist as it is usual before or soon after starting letrozole they will check the strength and thickness of your bones with a bone density scan.

It is common for people on hormone therapy such as both tamoxifen or letrozole to worry about the possibility hair thinning. This is usually mild and might only be for a short time. People don’t always tell their treatment team about hair thinning when they’re having hormone therapy so it’s difficult to say how common this is.

Talking to someone who has had a similar experience can be helpful too and our Someone Like Me service can arrange for one of our volunteers to talk to you by email or telephone. Our volunteers have had a personal experience of breast cancer and are trained to provide support. The Someone Like Me service would try and get a volunteer who has switched treatments.

You can ring the Someone Like Me team on 0345 077 1893 or email them at,so they can then match you to your volunteer.

Do call our Helpline if you would like to talk this through or have any further questions. Your call will be confidential, and the number is free from UK landlines and all mobile networks. The number is 0808 800 6000, (Relay UK -prefix 18001).

If you would like a nurse to call you do complete this form . Ticking the box agreeing to a call back.

Our opening hours are Monday to Friday 9am - 4pm and 9am -1pm on Saturday. Out of hours you can leave a message and we will call you back when we next open.

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Best wishes


Breast Care Nurse

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