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Led by Co-Chief Investigators, Professor Ramsey Cutress and Professor Michael Douek, the EndoNET Trial will evaluate the effectiveness of neoadjuvant endocrine treatment in postmenopausal women with early breast cancer.

EndoNET Trial logo

The EndoNET Trial is currently in Set-Up and is scheduled to begin recruitment by November 2021.

Trial Summary

There are 45,000 people who develop breast cancer each year in the UK, mostly women after their menopause and of a type known as oestrogen-receptor positive, HER-2 negative (human epidermal receptor-2). The current standard treatment is surgery within a month of diagnosis, followed by radiotherapy for some where required, and anti-hormone therapy (known as endocrine treatment) for 5-10 years. Most people will not need chemotherapy. Almost one-half will however be treated by surgical removal of the breast (mastectomy.) For others, lumpectomy (breast conservation surgery), will ensure that a only limited amount of breast tissue is removed. 

Anti-hormone therapy (Endocrine treatment) after surgery is very effective in the long-term treatment of breast cancer; it is however currently unknown whether it is also beneficial to start this same endocrine treatment before surgery, known as neo-adjuvant endocrine therapy. This study is to determine whether giving some of the endocrine therapy before surgery will shrink the tumour prior to operating. This could increase the rates of breast preservation by reducing the number of mastectomies for some women and the extent of surgery for others (removing less tissue leaves less defect). 

After mastectomy, many patients do not want or are unsuitable for breast reconstruction. Even if received, this may not always fully compensate for breast removal. Reducing the amount of breast tissue that has to be removed and increasing the rates of preserving breasts by treatment with neo-adjuvant endocrine therapy is therefore anticipated to improve cosmetic outcomes, leading to better quality of life. 

Patients with breast cancer are part of the study leadership team and others have been extensively consulted in the trial design. They indicated that overall quality of life and preserving the breast were the most important outcomes by which to measure study success. 

Patients in this controlled trial are allocated by chance to one of two groups, which determines their treatment. All patients will start hormone treatment on joining the trial: group 1 will have surgery within 31 days; group 2 will receive surgery after 6 months of neo-adjuvant endocrine therapy. People in group 2 will be closely monitored with an ultrasound scan at 3 months and 5 months to ensure continued response to this therapy prior to surgery. 

The EndoNET trial aims to recruit 1440 women from at least 30 NHS hospitals across the UK. Patients in both groups will complete quality of life questionnaires at intervals during their 15- month participation in the study and rates of breast conservation will be documented. The results will be published in medical journals and presented at international conferences. Patients could have the option of receiving the results too. 

Trial Schema

EndoNET Trial Schema

Trial Team

Michael Douek Ramsey Cutress Charles Malyon

Prof. Michael Douek
Co-Chief Investigator

Prof. Ramsey Cutress
Co-Chief Investigator

Charles Malyon
EndoNET Trial Manager


Contact Us 

Want to learn more? To contact the EndoNET Trial team, please send an email to

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