WoO: Window of Opportunity Trial of Olaparib and Durvalumab in Histologically Proven EOC

Inclusion Criteria: WoO pre-treatment (screening phase): 1. Patients with presumed and previously untreated advanced stage ovarian cancer planned to undergo laparoscopy for histologic diagnosis and treatment planning 2. Patients willing and able to comply with the study protocol for the duration of the study including undergoing treatment and scheduled visits and examinations including follow up 3. Patients able and willing to provide fresh frozen biopsy samples from laparoscopy as well as primary debulking for translational endpoints as well as serial liquid biopsies 4. Patients able and willing to provide formaldehyde-fixed paraffin embedded (FFPE) tissue samples from laparoscopy and primary debulking surgery 5. Patients aged ≥18 years 6. Patients must be capable of giving signed informed consent which includes compliance with the requirements and restrictions listed in the informed consent form (ICF) and in this protocol 7. Provision of signed and dated, written ICF for the mandatory biomarker and genetic re-search as well as the clinical/therapeutic part of the study prior to any mandatory study specific procedures, sampling, and analyses 8. Eastern cooperative oncology group (ECOG) performance status 0-1 (see Appendix 1) 9. Patients must have a life expectancy ≥16 weeks 10. Ability to take oral medication 11. Postmenopausal or evidence of non-childbearing status for women of childbearing potential (WOCBP): negative serum pregnancy test within 28 days of study treatment and confirmed neagtive urine or serum pregnancy test prior to treatment on day 1. Postmenopausal is defined as: * Amenorrheic for 1 year or more following cessation of exogenous hormonal treatments * Luteinizing hormone (LH) and Follicle stimulating hormone (FSH) levels in the post menopausal range for women under 50 * radiation-induced oophorectomy with last menses \>1 year ago * chemotherapy-induced menopause with \>1 year interval since last menses * surgical sterilisation (bilateral oophorectomy or hysterectomy) 12. Women of childbearing potential (WOCBP) and their partners, who are sexually active, must agree to the use of 2 highly effective forms of contraception in combination. This should be started from the signing of the informed consent and continue throughout the period of taking study treatment and for at least 6 months after last dose of study drug(s), or they must totally/truly abstain from any form of sexual intercourse. WoO treatment phase: 13. Confirmed advanced (FIGO IIB/III/IV) high-grade, non-mucinous, non-clear cell epithelial ovarian, fallopian tube or primary peritoneal cancer or known (BReast CAncer) BRCA mutation and any histologic type 14. Planned primary debulking surgery after confirmation of diagnosis and disease evaluation during laparoscopy 15. Body weight \>30kg 16. Patients must have normal organ and bone marrow function measured within 28 days prior to administration of study treatment as defined below: * Haemoglobin ≥10.0 g/dL with no blood transfusion in the past 28 days * Absolute neutrophil count (ANC) ≥1.5×10\^9/L * Platelet count ≥100×10\^9/L * Total bilirubin ≤1.5 × institutional upper limit of normal (ULN) * Aspartate aminotransferase (AST), serum glutamic oxaloacetic transaminase (SGOT) / alanine aminotransferase (ALT), serum glutamic pyruvate transaminase (SGPT) ≤2.5 × institutional upper limit of normal unless liver metastases are present in which case they must be ≤5×ULN. (cave: patients with intrahepatic metastases affecting liver function test might not be candidates for primary debulking surgery) * Patients must have creatinine clearance estimated of ≥51 mL/min using the Cockcroft-Gault equation or based on a 24 hour urine test: Estimated creatinine clearance=((140-age \[years\])\*weight (kg))/(serum creatinine (mg/dL)\*72)(\* 0,85) 17. Patients must have successfully contributed blood and tissue samples as per requirements. Exclusion Criteria: Medical conditions: 1. Disease requiring urgent surgical intervention 2. Evidence of significant uncontrolled concomitant disease that could affect compliance with the study protocol 3. Significant uncontrolled symptom burden (e.g. but not necessarily limited to large volume ascites, shortness of breath on exertion, pain requiring opioid medication, signs of (sub)ileus 4. Uncontrolled intercurrent illness, including but not limited to, ongoing or active infection, symptomatic congestive heart failure, recent (within 3 months) myocardial infarction, uncontrolled hypertension, unstable angina pectoris, cardiac arrhythmia, interstitial lung disease, uncontrolled major seizure disorder, unstable spinal cord compression, superior vena cava syndrome, serious chronic gastrointestinal conditions associated with diarrhea, or psychiatric illness/social situations that would limit compliance with study requirement, substantially increase risk of incurring AEs or compromise the ability of the patient to give written informed consent. 5. Other malignancy unless curatively treated with no evidence of disease for ≥5 years except: adequately treated non-melanoma skin cancer, curatively treated in situ cancer of the cervix, ductal carcinoma in situ (DCIS), stage 1, grade 1 endometrial carcinoma. Patients with a history of localized triple negative breast cancer may be eligible, provided they completed their adjuvant chemotherapy more than three years prior to registration, and that the patient remains free of recurrent or metastatic disease (optional criteria that is dependent on the patient population under investigation). 6. Resting electrocardiography (ECG) indicating uncontrolled, potentially reversible cardiac conditions, as judged by the investigator (eg., unstable ischemia, uncontrolled symptomatic arrhythmia, conges-tive heart failure, QTcF prolongation \>500 ms, electrolyte disturbances, etc.), or patients with congenital long QT syndrome. 7. Any unresolved toxicity NCI CTCAE