WinPro: This phase II trial is evaluating a combination of hormone treatments that may be useful for pre-surgery breast cancer treatmentAn open-label, randomized, window of opportunity study between diagnosis and definite surgery, to assess the effect of antiestrogen therapies, alone and in combination with microionized progesterone (prometrium) in patients with newly diagnosed ER+PR+ breast cancer

Inclusion

1. Post-menopausal women defined by any one of the following criteria;
a) Amenorrhea >12 months at the time of diagnosis and an intact uterus, with FSH and estradiol in the postmenopausal ranges,
b) prior bilateral oophorectomy, and
c) FSH and estradiol levels within the postmenopausal range (as per local practice) in women aged <55years who have undergone hysterectomy.
2. Histologically confirmed ER+ and PR+ breast cancers (defined as >10% positive staining cells)
3. HER2/CEP17 ratio of <2 (as per the ASCO CAP guidelines)
4. Tumour size >1cm as measured by ultrasound and/or mammogram
5. Ability to understand all patient information and informed-consent documents, written informed consent to participate in the trial, and to avail tissue and blood samples for research