A Pre-operative Window Study of Letrozole Plus PR Agonist (Megestrol Acetate) Versus Letrozole Alone in Post-menopausal Patients With ER-positive Breast Cancer

Inclusion Criteria

• •Histologically confirmed breast adenocarcinoma
• •Postmenopausal women
• •Core biopsy confirmation of invasive carcinoma on core biopsy, ≥T1c, either clinical NX or N0-N3
• •ER positive (Allred≥3) and HER2 negative
• •2 groups of patients are potentially eligible:
• •* Cohort A: Patients whose cancers have been deemed to be operable by the Multi-Disciplinary Team (MDT), with surgery planned for the next 2-6 weeks
• •* Cohort B: Patients with early or locoregionally advanced breast cancer planned for primary endocrine therapy, either in lieu of surgery or as neoadjuvant therapy prior to surgery- such patients must begin PIONEER trial therapy prior to starting any other endocrine therapy.
• •ECOG performance status of 0, 1 or 2
• •Adequate Liver, Renal and Bone marrow function, defined as:
• •* Adequate liver function where bilirubin is ≤1.5 x ULN
• •* Adequate renal function with serum creatinine ≤ 1.5 x ULN
• •* Adequate bone marrow function with ANC ≥1.0 x 10\*9/L and Platelet count ≥100 x 10\*9/L
• •Written informed consent to participate in the trial and to donation of tissue