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  • Research type

    Research Study

  • Full title

    Randomised Phase II clinical trial PIONEER- A Pre-operative wIndOw study of letrozole plus PR agonist (Megestrol Acetate) versus letrozole aloNE in post-menopausal patients with ER-positive breast cancer



  • Contact name

    Carrie Bayliss

  • Contact email

  • Sponsor organisation

    Cambridge University Hospitals NHS Foundation Trust and University of Cambridge

  • Eudract number


  • ISRCTN Number


  • Identifier


  • Duration of Study in the UK

    2 years, 5 months, 1 days

  • Research summary

    Around 75% of breast cancers are driven by expression and activity of Oestrogen receptor alpha (ERα). Standard treatment is ‘hormone’ therapy however clinical results vary considerably and a proportion of women with early breast cancer driven by ERα develop resistance to treatment, and relapse with incurable disease.
    Previously the interaction between ER (Oestrogen Receptors) and PR (Progesterone Receptors) was thought to be small and PR activity was thought to be just a passive effect of a working ER. Recent laboratory studies in breast cancer cells and animal studies have focused on this subject and have indicated that there may be a more important interaction between ER and PR; these studies suggest that targeting this interaction could have a significant effect on breast cancer results.
    This trial will investigate the effect of combining Megestrol acetate (a progesterone receptor activator) and Letrozole (an anti-oestrogen) which is a standard endocrine therapy for post-menopausal women. This is a 'window of opportunity' study treating and observing the patients in the two weeks prior to definitive surgery. The study is split into three treatment arms; one in which the patients receive only the standard anti-oestrogen treatment Letrozole; one in which they will receive a combination of Letrozole and low dose Megestrol acetate and the last which will receive Letrozole and high dose Megestrol acetate. This trial will be open to postmenopausal women with newly diagnosed, untreated, ER-positive, HER2 (human epidermal growth factor receptor 2) negative, invasive primary breast cancer.

  • REC name

    North East - Newcastle & North Tyneside 1 Research Ethics Committee

  • REC reference


  • Date of REC Opinion

    24 May 2017

  • REC opinion

    Further Information Favourable Opinion

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