RecruitingNot ApplicableInterventional

Does the timing and order of breast surgery and hormone treatment affect the quality of life and the amount of surgery required in post-menopausal women with breast cancer? The EndoNET study

Around 50,000 women in the UK are diagnosed with breast cancer each year. Most are past the menopause and have a type called oestrogen-receptor positive breast cancer. The usual NHS treatment is to have an operation within a few weeks of diagnosis, followed by hormone-blocking tablets for five to ten years. The EndoNET study is testing whether changing the order of treatment helps. Half the women in the study have surgery first as normal. The other half take standard hormone tablets (such as letrozole, anastrozole, or exemestane) for around six months before their operation. Researchers want to see if taking hormone tablets first can shrink the cancer. If it shrinks, surgeons might only need to remove the lump rather than the whole breast. This could help preserve more natural tissue, reduce surgical scars, and improve overall wellbeing.

At a glance

Status

Recruiting

Phase

Not Applicable

Sponsor

University of Oxford

Enrolment target

1,060

Start

23 Aug 2022

Estimated completion

30 Nov 2027

Newly diagnosed strongly ER-positive negative breast cancer

What is this study about?

Most breast cancers diagnosed after the menopause are fuelled by the hormone oestrogen. Standard NHS treatment usually begins with surgery within a month of diagnosis to remove the tumour. After the operation, many women take daily hormone tablets for several years to stop the cancer from returning. While this routine works very well, nearly half of women end up needing a full mastectomy, which is the removal of the entire breast.

The EndoNET trial is exploring whether starting hormone therapy before surgery could lead to better outcomes. Instead of operating straight away, doctors give patients daily hormone tablets for about six months. The hope is that the medicine will shrink the tumour before the surgeon operates. If the lump becomes smaller, surgeons may be able to perform a lumpectomy (removing just the tumour) rather than removing the whole breast.

Saving healthy breast tissue can make a large difference to a woman's physical recovery, body confidence, and emotional wellbeing. By directly comparing the traditional 'surgery first' approach with the 'tablets first' approach, this study hopes to provide clear evidence on which sequence gives women the best cosmetic results and overall quality of life, without compromising their cancer care.

Key takeaways

The EndoNET study tests whether taking hormone tablets before breast surgery can safely shrink tumours.
A smaller tumour may allow surgeons to perform a lumpectomy rather than removing the entire breast.
Participants take standard, well-tested NHS hormone tablets such as letrozole, anastrozole, or exemestane.
Women having tablets before surgery receive regular ultrasound checks to ensure the cancer is responding.
Taking part lasts for 15 months and involves answering questionnaires about your wellbeing.

Who may be eligible?

This trial is designed for women who have gone through the menopause and have recently been diagnosed with a single breast cancer tumour measuring at least 15 millimetres across.

To take part, your tumour must be strongly oestrogen-receptor positive (ER+) and HER2-negative. This means the cancer cells are driven by oestrogen and respond well to hormone therapy. It also means you are unlikely to need chemotherapy as part of your care.

You will need to be well enough to have surgery and radiotherapy, and able to attend routine hospital check-ups and fill out short surveys about your health over a 15-month period.

Could this study suit you?

Answer these quick questions to see if you may be eligible. This is a guide only — the research team makes the final call.

I am a woman who has gone through the menopause.
I have been newly diagnosed with a single breast cancer tumour (15 mm or larger).
My cancer is strongly oestrogen-receptor positive (ER+) and HER2-negative.
My doctor has confirmed that I do not need chemotherapy.
I am suitable and willing to have surgery and radiotherapy.
I am able to attend hospital monitoring visits and complete short health surveys.

Answer every question to see your result.

What does participation involve?

If you take part, you will be placed into one of two groups by chance. One group has standard surgery within 2 to 8 weeks of joining, followed by daily hormone tablets. The other group starts daily hormone tablets straight away and has their operation around six months later. The tablets used (letrozole, anastrozole, or exemestane) are standard NHS treatments taken once a day. If you are in the six-month tablet group, you will have regular clinic visits and ultrasound scans at 6 weeks, 3 months, and 5 months to check how the tumour is responding. You will also be asked to complete quality-of-life questionnaires at several points over 15 months. There is also an optional sub-study that involves giving a single morning fasting blood sample to look at insulin levels.

Potential risks and benefits

Taking hormone tablets first may shrink your tumour, which could allow for a smaller operation and preserve more of your natural breast tissue. The medicines used are the same standard tablets used in everyday NHS cancer care, with well-known side effects such as hot flushes, tiredness, and joint stiffness. If you take the tablets before surgery, doctors will check your tumour closely with ultrasound scans; if it is not shrinking, they can arrange your operation without unnecessary delay. Taking part is completely voluntary, and you are free to leave the trial at any point without it affecting your standard NHS care.

Locations (44)

Aberdeen Royal Infirmary
Approximate
Aberdeen, Scotland
Royal Devon & Exeter Hospital
Approximate
Exeter, England
Belfast City Hospital
Approximate
Belfast, Northern Ireland
Southampton General Hospital
Approximate
Southampton, England
University Hospital Llandough
City only
Penarth, Wales
Churchill Hospital
Unverified
Oxford, England
Royal Albert Edward Infirmary
Unverified
Wigan, England
Basildon University Hospital
Unverified
Basildon, England
Southend University Hospital
Unverified
Westcliff-on-Sea, England
Southmead Hospital
Unverified
Bristol, England
Nottingham City Hospital
Unverified
Nottingham, England
Royal Hampshire County Hospital
Unverified
Winchester, England

Common questions

Will waiting six months for surgery allow my cancer to spread?

Hormone tablets work quickly to slow down or stop the growth of oestrogen-fuelled cancer cells. Your team will monitor you closely with regular ultrasound scans. If there is any sign the tablets are not working, your surgery will be scheduled straight away.

What medicines will I take?

You will take a standard hormone therapy tablet once daily, such as letrozole, anastrozole, or exemestane. These are all widely used and approved NHS cancer treatments.

Do I have to take part in the extra blood test study?

No. The Trans-EndoNET sub-study, which looks at blood insulin levels, is entirely optional. You can say no to the blood test and still take part in the main study.

Who decides what operation I have?

You and your breast surgeon will decide together whether a lumpectomy or a mastectomy is the best and safest choice for you, based on how much the tumour has shrunk and your personal preferences.

Will I need chemotherapy if I join this trial?

This study is specifically for women whose cancer type means chemotherapy is not expected to be part of their treatment plan.

How to find out more

Surgical Interventions Trials Unit (SITU)

endonet@nds.ox.ac.uk +44 (0)1865 223464 Official trial record

Always speak to your GP or specialist before deciding to take part in a study.