A trial looking at letrozole after hormone therapy for early breast cancer in postmenopausal women - SOLE

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

Cancer type:

Breast cancer




Phase 3

This trial is looking at treatment with letrozole (Femara) for early breast cancer that has tested positive for hormone receptors in post menopausal Open a glossary item women. The trial is comparing having letrozole all the time with stopping and starting treatment.

The first treatment for early breast cancer is usually surgery. After surgery, women who have hormone receptor positive breast cancer will have hormone therapy as part of their treatment. Most women have hormone therapy for at least 5 years. This helps to reduce the risk of breast cancer coming back. But there is still a small risk the cancer could come back. And doctors are always looking for a way to decrease this risk.

Letrozole is an aromatase inhibitor. Aromatase inhibitors are a type of hormone therapy for women who are past their menopause. We know from research it may help to stop breast cancer coming back if you have letrozole for 5 years after your first 5 years of hormone therapy.

The results of a small study show that having intermittent letrozole may be as good as, or better than having it continuously. The researchers want to look at this in a larger trial.

The aim of this trial is to compare intermittent and continuous letrozole for postmenopausal women for an additional 5 years after their first 5 years of hormone therapy.

Who can enter

You can enter this trial if you

  • Had surgery to remove your breast cancer
  • Had cancer that had spread to the lymph nodes Open a glossary item in the armpit or in the breast
  • Had hormone receptor positive breast cancer
  • Are post menopausal or have had both your ovaries removed (bilateral oophorectomy) – you may also join the trial if you had radiation to both your ovaries to stop your periods and have not had a period for at least 3 months
  • Had 4 to 6 years of hormone therapy after surgery and have finished it in the last 12 months
  • Have satisfactory blood test results

You cannot enter this trial if you

  • Had inflammatory breast cancer
  • Had cancer in both breasts – bilateral breast cancer
  • Had breast cancer that has spread to another part of the body
  • Had cancer that had spread to the lymph nodes above the collar bone
  • Had a break or crack (fracture) due to thinning of the bones (osteoporosis) during your hormone therapy
  • Are taking hormone replacement therapy Open a glossary item (HRT)
  • Are having drugs called bisphosphonates – you may join the trial if you are taking them for thinning of the bones
  • Have had another cancer – you may join the trial if you had basal or squamous cell skin cancer or carcinoma in situ Open a glossary item of the cervix, bladder or breast that has been successfully treated
  • Have any other medical condition that could affect you taking part in this trial

Trial design

This is a phase 3 trial. It is an international trial and will recruit 4,800 women from centres around the world. It is a randomised trial. You will be put into 1 of 2 groups. Neither you nor your doctor can choose which you group you are in.

Everyone taking part in the trial will have letrozole for 5 years. Letrozole is a tablet you take it once a day.

If you are in group 1, you take letrozole continuously for 5 years.

If you are in group 2, you take letrozole for 9 months and then don’t take it for 3 months of the year. You do this for 4 years. For year 5 you take it for the whole year.

Hospital visits

You will see the doctor and have some tests before starting treatment. These tests include

You see the breast team every 6 months for 5 years for a physical examination. You have a mammogram once a year. After 5 years you then see the breast team every year.

Side effects

The most common side effects of letrozole include

You can find more information about 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

Professor A M Thompson

Supported by

Breast International Group (BIG)
Experimental Cancer Medicine Centre (ECMC)
International Breast Cancer Study Group (IBCSG)
NIHR Clinical Research Network: Cancer

Questions about cancer? Contact our information nurses

Freephone 0808 800 4040

Last review date

CRUK internal database number:

Oracle - 2557

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

Picture of Harriet

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

Last reviewed:

Rate this page:

Currently rated: 4 out of 5 based on 1 vote
Thank you!
We've recently made some changes to the site, tell us what you think

Share this page