EndoNET: Randomised controlled trial evaluating effectiveness of neoadjuvant endocrine treatment in post-menopausal women with breast cancer


EndoNET is a Phase III, randomised, controlled trial evaluating whether a period of endocrine therapy prior to surgery (neoadjuvant endocrine therapy) reduces surgical burden and better health-related quality of life (QoL) for post-menopausal women with ER+, HER2- invasive breast cancer who do not require chemotherapy.



To evaluate whether 6 (+/-1) months of neo-adjuvant endocrine therapy reduces surgical burden resulting in better HRQoL over 15 months and higher rates of breast conservation surgery (BCS) for post-menopausal women with >T1, strongly ER+, HER2- invasive breast cancer who do not require chemotherapy.


  1. Disease free survival/recurrence
  2. Ki67 evaluation in NET setting
  3. Other surgical outcomes
  4. Other patient-reported outcome measures (PROMs).


Key inclusion criteria:

  • Post-menopausal women
  • Unifocal Breast Cancer visible on ultrasound
  • Strongly ER+, HER2-
  • T-stage 2 or 3 (> 2cm)
  • Axillary N0-1 on diagnostic USS +/- negative FNA or core biopsy
  • Unlikely to require chemotherapy.


Planned sample size:

1,440 participants (720 per arm) will be randomised (1:1) to either to the comparator arm (pre-surgical ET, surgery at 2-4 weeks) or the intervention arm (NET, surgery at 6 months).


Total number of sites planned:

Approximately 50 sites planned.

EndoNET is open to new sites and would welcome expressions of interest by contacting the study team on endonet@nds.ox.ac.uk.



Planned recruitment period is from August 2022 to June 2025 with a long-term follow up of up to 20 years (subject to additional funding and/or resource).


Contact information and website:

You can contact the study team on endonet@nds.ox.ac.uk or find out more information on our website: https://www.nds.ox.ac.uk/research/surgical-intervention-trials-unit/the-endonet-trial.