Preoperative Olaparib Endometrial Carcinoma Study (POLEN)

Inclusion Criteria: * Patients must have histologically-confirmed type I primary endometrial carcinoma (EC). Diagnosis biopsy must contain 3-12 mg of tumour cellularity/stroma (Tumour: 5-20 mm) and this will be checked in the central laboratory for this trial. If tumour cellularity/stroma is inadequate, one re-biopsy with adequate tumour cellularity/stroma will be mandatory before study entry. * WHO performance status ≤ 2. * Adequate bone marrow function as shown by: ANC ≥ 1.5 x 109/L, Platelets ≥ 100 x 109/L, Hb \>10g/dL. * Adequate liver function as shown by: serum bilirubin ≤ 1.5 x ULN INR \< 1.3 (or \< 3 on anticoagulants) ALT and AST ≤ 2.5x ULN * Adequate renal function: serum creatinine ≤ 1.5 x mg/dL. * Fasting serum cholesterol ≤300 mg/dL or ≤7.75 mmol/L and fasting triglycerides ≤ 2.5 x ULN. * Signed informed consent, including consent to tissue collection and blood samples as specified by the protocol. Exclusion Criteria: * Subjects who have received prior anticancer therapies for the current endometrial cancer (including chemotherapy, radiotherapy, antibody based therapy, hormonotherapy or surgery). * Patients, who have had a major surgery or significant traumatic injury within 4 weeks of start of study drug, patients who have not recovered from the side effects of any major surgery (defined as requiring general anesthesia) or patients that may require major surgery during the course of the study. * Prior treatment with any investigational drug within the preceding 4 weeks. * Patients receiving chronic, systemic treatment with corticosteroids or another immunosuppressive agent, except corticosteroids with a daily dosage equivalent to prednisone ≤ 20 mg. However, patients receiving corticosteroids must have been on a stable dosage regimen for a minimum of 4 weeks prior the study entry. Topical or inhaled corticosteroids are allowed. * Patients who have received immunization with attenuated live vaccines within one week of study entry (note: during study period these kind of vaccines are also not allowed). * Patients who have any severe and/or uncontrolled medical conditions or other conditions that could affect their participation in the study such as: Symptomatic congestive heart failure of New York heart Association Class III or IV Unstable angina pectoris, myocardial infarction within 6 months of start of study drug, Serious uncontrolled cardiac arrhythmia or any other clinically significant cardiac disease Severely impaired lung function Uncontrolled diabetes as defined by fasting serum glucose \>1.5 x ULN Active (acute or chronic) or uncontrolled severe infections Liver disease such as cirrhosis, chronic active hepatitis or chronic persistent hepatitis A known history of HIV seropositivity. * Patients with an active, bleeding diathesis. * Female patients who are pregnant or breast feeding, or adults of reproductive potential who are not using effective birth control methods. If barrier contraceptives are being used, these must be continued throughout the trial by both sexes. Hormonal contraceptives are acceptable as a sole method of contraception. (Women of childbearing potential must have a negative urine or serum pregnancy test within 7 days prior to administration of AZD2281). * History of noncompliance to medical regimens. * Patients unwilling to or unable to comply with the protocol.