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Oestrogen positive breast and endometrial cancers

EJM60
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In 2016/17 I was treated for oestrogen positive breast cancer and had surgery, radiotherapy and am still taking anastrozole. I have recently had a total hysterectomy for endometrial cancer and the histology has come back that it is oestrogen positive. I’m a little bit concerned as my thought are that the anastrozole should have removed oestrogen from my body, thus preventing another oestrogen positive cancer. Does this mean that the anastrozole isn’t effective for me? Any information you can give me would be gratefully received. 

  • Dear EJM60

    Thank you for getting in touch. My name is Fiona and I’m one of the Cancer Information Nurse Specialists here on the Macmillan Support Line. I see that you’re also a member of several forums, I hope that you’re finding them to be a supportive space for you.

    I’m sorry to hear that you’ve had a second cancer diagnosis. This must be a worrying time for you, it is understandable that you have questions about this.

    Unfortunately, whilst we know that hormone therapy significantly reduce the risk of developing a breast cancer recurrence their role in endometrial cancers is less well understood. Other factors are thought to be involved in the development of endometrial cancer, in particular if there is a genetic mutation present, such as BRCA 1 or BRCA 2.

    Anastrazole, as you probably know, is one of a group of drugs called aromatase inhibitors (AIs). AIs interfere with the production process of oestrogen by the body’s adrenal glands. Another kind of hormone therapy is tamoxifen which works differently, in that it prevents oestrogen from attaching to cancer cells but both can reduce the risk of breast cancer recurrence.

    We know that tamoxifen can cause thickening of the endometrial lining and that there can be a risk of developing endometrial cancer from this in approximately 2 out of 1000 cases. The risk of developing endometrial cancer when having anastrazole if thought to be significantly lower but it can happen.

    I hope that has helped, but it would be worth having a discussion with your Consultant if you have any further questions about this.

    Best wishes,

    Fiona S

    Cancer Information Nurse Specialist

    Ref: FS/KM

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