Difference between Zoladex and Anastrozole versus Tamoxifen

I have been on Zoladex and Anastrozole for 4 years and am due to switch to Tamoxifen in mid 2026. Please could I have a bit of information about these differences and any changes in side effects anyone may have experienced? 


 The Zoladex and Anastrozole have been hell and has left me with a massive amount of weight gain which doesn’t go away despite trying many methods, and treatment resistant depression which has been awful. Alongside many other horrible side effects which nobody offers any kind of support for. I’ll then be on Tamoxifen for another 5 years. 

  • Hi rmscj and thank you for your post.

    I am sorry to hear about the treatment you are receiving for breast cancer and the ongoing side effects you have been suffering with since. It’s completely understandable to have questions about changing your treatment.

    You’ve been on Zoladex and Anastrozole for four years, and moving to Tamoxifen can feel like a big step. These medicines all help stop oestrogen from feeding certain types of breast cancer, but they work in slightly different ways.

    Zoladex stops your ovaries from making oestrogen (a hormone that can help some breast cancers grow). Whilst Anastrozole lowers the amount of oestrogen in your body.

    Tamoxifen works differently – it blocks oestrogen from reaching the cancer cells.

    Some people notice changes in side effects when they switch. For example, joint pain might ease a little on Tamoxifen, but hot flushes or tiredness can still happen. Everyone reacts differently, so it’s hard to say exactly how you’ll feel.

    You may find Macmillan’s webpage on weight gain following cancer treatment useful to read.

    I’m not sure what treatment you have had for your depression. Some people find counselling can help.

    We have information on how to find a counsellor on our webpage.

    The organisation Breast Cancer Now have some helpful information on some of the feelings that women have after a breast cancer diagnosis. They do have a service called  'Someone like me' where they may be able to put you in touch with another person going through similar things.

    There are Maggies centres in certain parts of the UK that provide emotional support to people affected by cancer. Many of their centres have trained psychologists who can provide one-to-one or group counselling. You do not need to live near a Maggies centre as you can call your nearest one for advice.

    Hopefully a change in treatment may help with your treatment resistant depression.  

    I hope that you will find Tamoxifen more manageable, with fewer side effects that are easier to handle.

    Please get back to us if you need any more information or support

    It might help to talk things through with one of our nurses on the helpline. You can call for free on 0808 800 4040, Monday to Friday, 9am to 5pm.

    Kind regards,

    Tina