A trial looking at anastrozole to prevent breast cancer in post-menopausal women (IBIS II Prevention)

This trial aims to find out if anastrozole (Arimidex) can be used to prevent breast cancer in women who are at 'high risk' of developing this disease.

Over 47,000 women in the UK are diagnosed with breast cancer every year. Improvements have been made in recent years in the treatment of breast cancer, and more cancers are being diagnosed early through the NHS screening programme . But we need to know more about how to prevent breast cancer.

Women who have been through the menopause don’t produce any oestrogen from their ovaries. But they do produce some from their adrenal glands. Oestrogen is known to encourage breast cancer cells to grow, so stopping its production may help prevent breast cancer.

Anastrozole is a drug that stops oestrogen being made by the adrenal glands. It is used as a treatment to help stop breast cancer coming back in women who have had their menopause.

In this trial (called IBIS II), anastrozole or a placebo ('dummy' tablet) will be given to post-menopausal women who are at a ‘high risk’ of developing breast cancer. The doctors hope that it might help prevent breast cancer from developing in these women.

Recruitment

Start 25/05/2003

End 31/12/2010

Phase

Phase 3

Who can enter

You can enter this trial if you

Are aged between 40 and 70
Have been through your menopause
Have not been diagnosed with breast cancer
Have had DCIS treated by mastectomy within the last 6 months
Have a ‘high risk’ of developing breast cancer

You cannot enter this trial if you

Are still having periods
Have breast cancer, or have had breast cancer in the past (unless you have had DCIS - see criteria for specific age groups)
Have had any other cancer in the last 5 years (except non-melanoma skin cancer or carcinoma in situ of the cervix)
Are currently having tamoxifen or raloxifene, or have had tamoxifen or raloxifene for more than 6 months in the last 5 years (women who took part in the IBIS I (IBIS 1) trial will be able to take part if they stopped treatment in this trial more than 5 years ago)
Want to carry on taking HRT (hormone replacement therapy) that contains oestrogen
Have had (or are planning to have) your breast(s) removed (a mastectomy) to try and prevent breast cancer
Have any other serious medical conditions
Have taken any other drug as part of a clinical trial within the last 3 months

There is more detailed information about 'high risk' in our page on the IBIS II prevention trial in the questions and answers section.

Trial design

This is a randomised trial. It has 2 groups. The people taking part will be put into the groups by a computer. The trial will recruit 6,000 women.

The people in group 1 will take anastrozole once a day for 5 years. The people in group 2 will take a dummy tablet (placebo) once a day for 5 years. You will not know if you are taking the anastrozole or the placebo. Neither will the doctors and nurses at the hospital.

Whichever group you are in, you may be asked to take part in the Bone sub study (which is part of the main prevention trial). This aims to test the effects of anastrozole on your bones. Women who are asked to take part in this sub study must have been off HRT for 1 year before entering the trial.

Hospital visits

You will need to go to hospital for tests before you start taking part in the trial. This will include a mammogram (and maybe a biopsy to make sure you don’t have breast cancer). You will then have a mammogram at least once every 2 years (the frequency will vary slightly between hospitals).

You will have a blood test done before you start the trial, and again after 1 year and 5 years.

Before you start the trial, you will have a bone density scan (called a DXA or DEXA scan) and two spinal xrays to check that your bones are not fragile.

If you take part in the Bone sub study, you will have a bone density scan 1, 3, 5 and 7 years after starting the trial to check for changes in the bones.

All women will be asked to go to the hospital to see a doctor after 6 months and 1 year of joining the trial. You will then see the doctor at least every year, but maybe more often (again, this will vary slighty between hospitals). A local trial coordinator will contact you every 6 months to check on you and to give you support and advice.

Side effects

As with all treatments, anastrozole has some side effects. These include

Hot flushes
Vaginal dryness
Hair thinning
Carpal tunnel syndrome

More unusual side effects are

Sickness
Weight loss
Diarrhoea
Tiredness
Headache
Skin rash

If you do have problems with side effects, you may be able to take the tablet every other day rather than every day. It may also be possible to stop taking it for a while (maybe for 1-3 months), with the consent of the trial doctors.

There is more information about this trial on the IBIS II trial website.