Letrozole for Estrogen/Progesterone Receptor Positive Low-grade Serous Epithelial Ovarian Cancer (LEPRE Trial)

Inclusion Criteria: I - 1. Age ≥ 18 years. I - 2. Newly diagnosed, low-grade serous carcinoma of the ovary including cancer of fallopian tube and peritoneum (invasive micropapillary serous carcinoma or invasive grade 1 serous carcinoma). This is to be confirmed via nuclear p53 immunohistochemistry testing by a central pathology review performed at the Coordinating Centre. I - 3. Immunohistochemically determined positivity (≥ 10%) for ER and/or PgR expression. This is to be confirmed by centralized review. I - 4. Patients must have undergone an upfront surgery with maximal cytoreductive effort, with either optimal or suboptimal residual disease status. I - 5. Stage III-IV according to 2018 FIGO classification. For proper staging: * Patients must have undergone contrast-enhanced CT-scan of the chest, abdomen and pelvis within 28 days prior to randomization. If CT-scan is not recommended (e.g. for allergy to contrast agent) MRI or 18F-FDG PET/CT-scan are allowed. * The imaging evaluation must be accompanied by an anamnestic and physical examination within 14 days prior to randomization. I - 6. Postmenopausal, defined as any of the following criteria: * Patients who underwent bilateral salpingo-oophorectomy; * Monolateral salpingo-oophorectomy, amenorrhea for 12 or more consecutive months and age ≥60 years; * Monolateral salpingo-oophorectomy, amenorrhea for 12 or more consecutive months, age \<60 years and FSH and serum estradiol levels within the laboratory's reference r…