Adjuvant Therapy in POLE-Mutated and p53-Wildtype/NSMP Early Stage Endometrial Cancer RAINBO BLUE & TAPER

Inclusion Criteria:

• Patients must have had surgery consisting of hysterectomy and bilateralsalpingo-oophorectomy. Lymph node dissection can be performed as per institutionalstandards. There must be no macroscopic residual disease after surgery.

• Patients must have histologically confirmed Stage I to III endometrial carcinomawhich can be endometrioid, serous, clear cell, un/dedifferentiated, carcinosarcomaor mixed.

• Patients' Eastern Cooperative Group (ECOG) performance status must be 0, 1, or 2.

• HIV-infected patients on effective anti-retroviral therapy with undetectable viralload within 6 months are eligible for this trial.

• Patients' age must be ≥ 18 years.

• Patient consent must be appropriately obtained in accordance with applicable localand regulatory requirements.

• Patient is able (i.e. sufficiently fluent) and willing to complete thepatient-reported outcomes (PRO) questionnaires in either English, French or avalidated language

• Patients must be accessible for treatment and follow-up. Patients enrolled on thistrial must be treated and followed at the participating centre

• Protocol treatment is to begin within 10 weeks of hysterectomy/bilateralsalpingo-oophorectomy

Exclusion Criteria:

• Prior Neoadjuvant chemotherapy for current endometrial cancer diagnosis.

• Prior pelvic radiation.

• Patients with a history of other malignancies, except: carcinoma in-situ withoutevidence of invasive disease when resected, adequately treated non-melanoma skincancer, or other tumours curatively treated with no evidence of disease for ≥ 5years.

• Clinical evidence of distant metastasis as determined by pre-surgical orpost-surgical imaging (CT scan of chest, abdomen and pelvis or whole-body PET-CTscan)

• Patients with a documented positive surgical margin.

• Patients with a documented positive peritoneal washings, if performed.