A trial looking at low dose oestrogen to treat advanced breast cancer after menopause

Please note - this trial is no longer recruiting patients. We hope to add results when they are available.

Cancer type:

Breast cancer




Phase 2

This trial is looking at the female hormone Open a glossary item oestrogen (‘estradiol’) to treat advanced breast cancer that is no longer responding to hormone treatments called aromatase inhibitors.

Oestrogen can kill breast cancer cells as long as they haven’t been exposed to high levels before. Doctors used to use this treatment and it worked because your body stops making most of its oestrogen at menopause. So breast cancer that develops after menopause won’t have been exposed to high levels. High doses of oestrogen have unpleasant side effects, so doctors started using drugs like tamoxifen, or aromatase inhibitors to treat breast cancer instead.

Breast cancer cells can stop responding to treatment after a while. Doctors call this ‘resistance’. Researchers want to find a way of treating breast cancer that has become resistant to hormone therapies. One way of doing this is by attacking the cancer cells with treatments that haven’t been used before.

We know from research that doctors may be able to use a lower dose of oestrogen than they used to use to kill breast cancer cells. If you have had a course of aromatase inhibitors after your menopause, your oestrogen level will be much lower than normal menopause levels. So, the amount of oestrogen you need to affect your cancer will be lower too. This means fewer side effects. The aim of this trial is to see if using oestrogen in this way will help treat people with advanced post menopausal breast cancer.

Who can enter

You can enter this trial if you

  • Are a woman with breast cancer and have permanently stopped having periods for over a year (you are post menopausal)
  • Have breast cancer with receptors for oestrogen or progesterone or both (ER or PR positive)
  • Have breast cancer that has spread (metastasised Open a glossary item) or come back in the same area (local recurrence), but cannot be removed with surgery
  • Have breast cancer that was controlled or shrunk by an aromatase inhibitor for at least 6 months before it came back
  • Will have finished taking an aromatase inhibitor Open a glossary item no more than 4 weeks before the start of the trial (please note, don’t stop taking prescribed medication without talking to your doctor)
  • Have cancer that can be treated with more hormone therapy
  • Are well enough to take part (performance status 0, 1, 2)
  • Have satisfactory blood tests

You cannot enter this trial if you

  • Have cancer that has only spread to your bones (bone metastases)
  • Have cancer that is spreading quickly to large organs such as your liver, heart, stomach, lungs or intestines
  • Have had any other cancer except carcinoma in situ of the cervix or non melanoma skin cancer that has been removed with surgery
  • Have had surgery or radiotherapy in the month before the trial starts and have not recovered yet
  • Have had chemotherapy, biological therapy or hormone therapy within 4 weeks of the start of the trial
  • Have ever had a blood clot in your veins (deep vein thrombosis) or lungs (pulmonary embolism)
  • Have had heart problems such as uncontrolled chest pain (unstable angina) or your heart not pumping blood properly (heart failure)
  • Are taking medication which may affect the trial drugs - you can check this with your doctor

Trial design

This trial will recruit up to 50 patients. There are 3 stages, each with a slightly different treatment. Everyone will start at stage one. The 3 treatment stages are

  • Low dose oestrogen
  • High dose oestrogen
  • An aromatase inhibitor Open a glossary item

Everyone will take low dose oestrogen (estradiol) until it stops helping. You then have the option to try high dose oestrogen if your doctor thinks this may help treat your disease. If oestrogen doesn’t help to treat your cancer, you will stop the trial.

If either dose of oestrogen helps to treat your cancer, you will go back to having the aromatase inhibitor you were taking before the start of the trial. This is because the oestrogen may have made your cancer sensitive to aromatase inhibitors again.

When you stop the trial, you will continue to see your regular cancer doctor.

You fill out a questionnaire before you start treatment and then every few months during your treatment. The questionnaire will ask you about any side effects you have had and about how you have been feeling. This is called a quality of life study.

Hospital visits

Before you start the trial you will see the doctor and have some tests. These tests include

  • Physical examination
  • Blood tests
  • Heart trace (ECG Open a glossary item)
  • Chest X-ray
  • CT scan or MRI scan

On the day you start the trial, you will see the doctor and have a blood test. You also fill out a quality of life study. Two hours after your first dose of oestrogen, you have another blood test.

For the next 3 months, you see your doctor once a month. You have a blood test and complete another quality of life study each time. You then see your doctor every 3 months for another blood test and quality of life study.

You will repeat this pattern of hospital visits (except the pre trial tests) for each new treatment stage you enter.

After the trial has finished, you will continue to see you own doctor as you did before.

Side effects

Researchers expect that you should generally cope well with low dose oestrogen. But there are possible side effects including

There is also an increased risk of womb cancer, and a very small increased risk of having another new breast cancer. The risks increase the longer you take estradiol. It is unlikely that you will take estradiol for long enough to increase these risks. You will have regular breast examinations as part of the trial.

You can find out more about the aromatase inhibitors Open a glossary item such as anastrazole, exemestane and letrozole on CancerHelp UK.

Recruitment start:

Recruitment end:

How to join a clinical trial

Please note: In order to join a trial you will need to discuss it with your doctor, unless otherwise specified.

Please note - unless we state otherwise in the summary, you need to talk to your doctor about joining a trial.

Chief Investigator

Dr Sacha Howell

Supported by

Experimental Cancer Medicine Centre (ECMC)
The Christie NHS Foundation Trust

Questions about cancer? Contact our information nurses

Freephone 0808 800 4040

Last review date

CRUK internal database number:

Please note - unless we state otherwise in the summary, you need to talk to your doctor about joining a trial.

Harriet wanted to try new treatments

A picture of Harriet

“I was keen to go on a clinical trial. I wanted to try new cancer treatments and hopefully help future generations.”

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