Refining Adjuvant Treatment IN Endometrial Cancer Based On Molecular Features

Participants of the four RAINBO trials should be eligible according to the inclusion and exclusion criteria of both the overarching RAINBO trials program and the clinical trial that they are assigned to based on the molecular profile. Inclusion Criteria of the overarching RAINBO program: * Histologically confirmed diagnosis of endometrial cancer (EC) of the following histotypes: endometrioid endometrial carcinoma, serous endometrial carcinoma, uterine clear cell carcinoma, dedifferentiated and undifferentiated endometrial carcinoma, uterine carcinosarcoma and mixed endometrial carcinomas of the aforementioned histotypes. * Full molecular classification performed following the diagnostic algorithm described in WHO 2020 (5th Edition, IARC, Lyon, 2020) * TLH-BSO or TAH-BSO with or without lymphadenectomy or sentinel node biopsy, without macroscopic residual disease after surgery * No distant metastases as determined by pre-surgical or post-surgical imaging (CT/MRI scan of chest, abdomen and pelvis or PET-CT scan) * Age ≥ 18 years * Expected start of adjuvant treatment (if applicable) within 10 weeks after surgery * Patients must be accessible for treatment and follow-up * Written informed consent for participation in one of the RAINBO trials, permission for the contribution of a tissue block for translation research and permission for the use and sharing of data for the overarching research project according to the local Ethics Committee requirements. Exclusion Criteria overarching RAINBO program: * History of another primary malignancy, except for non-melanoma skin cancer, in the past 5 years * Prior pelvic radiation The MMRd-GREEN trial Inclusion criteria: * Written informed consent * WHO Performance score 0-1 * Histologically confirmed FIGO 2009 stage IB/II with LVSI, stage III, or stage IV with limited pelvic peritoneal involvement (FIGO 2023 stage IB with LVSI, stage II with myometrial or cervical stroma involvement and LVSI, or stage III disease) * Molecular classification: MMRd EC\* * No prior pelvic radiotherapy * Body weight \> 30 kg * Adequate systemic organ function: * Creatinine clearance (\> 40 cc/min): Measured creatinine clearance (CL) \>40 mL/min or Calculated creatinine CL\>40 mL/min by the Cockcroft-Gault formula (Cockcroft and Gault 1976) or by 24-hour urine collection for determination of creatinine clearance. * Adequate bone marrow function : hemoglobin \>9.0 g/dl, Absolute neutrophil count (ANC) ≥1.0 x 109/l, platelet count ≥75 x 109/l. * Adequate liver function: Bilirubin ≤1.5 x institutional upper limit of normal (ULN). \<\<This will not apply to patients with confirmed Gilbert's syndrome (persistent or recurrent hyperbilirubinemia that is predominantly unconjugated in the absence of hemolysis or hepatic pathology), who will be allowed only in consultation with their physician.\>\> * ALT (SGPT) and/or AST (SGOT) ≤2.5 x ULN Exclusion criteria: * Major surgical procedure (as defined by the Investigator) within 28 days prior to the first dose of Investigational medicinal product (IMP). * History of allogenic organ transplantation. * Uncontrolled intercurrent illness, including but not limited to, ongoing or active infection, symptomatic congestive heart failure, uncontrolled hypertension, unstable angina pectoris, cardiac arrhythmia, interstitial lung disease, 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. * Any previous treatment with a PD(L)1 inhibitor, including durvalumab. * Receipt of live attenuated vaccine within 30 days prior to the first dose of durvalumab. Note: Patients, if enrolled, should not receive live vaccine whilst receiving IP and up to 30 days after the last dose of IMP. * Current or prior use of immunosuppressive medication within 14 days before the first dose of durvalumab with the exceptions of : * Intranasal, inhaled, topical steroids, or local steroid injections (e.g., intra articular injection). * Systemic corticosteroids at physiologic doses not to exceed \<\<10 mg/day\>\> of prednisone or its equivalent. * Steroids as premedication for hypersensitivity reactions (e.g., CT scan premedication). * History of active primary immunodeficiency * Active or prior documented autoimmune or inflammatory disorders (including inflammatory bowel disease \[e.g., colitis or Crohn's disease\], diverticulitis \[with the exception of diverticulosis\], systemic lupus erythematosus, Sarcoidosis syndrome, or Wegener syndrome. The following are exceptions to this criterion: * Patients with vitiligo or alopecia * Patients with hypothyroidism (e.g., following Hashimoto syndrome)stable on hormone replacement * Any chronic skin condition that does not require systemic therapy * Patients without active disease in the last 5 years may be included but only after consultation with the study physician. * Active infection including tuberculosis (clinical evaluation that includes clinical history, physical examination and radiographic findings, and TB testing in line with local practice), hepatitis B (known positive HBV surface antigen (HBsAg) result), hepatitis C, or human immuno-deficiency virus (positive HIV 1/2 antibodies). Patients with a past or resolved HBV infection (defined as the presence of hepatitis B core antibody \[anti-HBc\] and absence of HBsAg) are eligible. Patients positive for hepatitis C (HCV) antibody are eligible only if polymerase chain reaction is negative for HCV RNA. * Medical or psychological condition which in the opinion of the investigator would not permit the patient to complete the study or sign meaningful informed consent.