FUlvestrant in Gynecological Cancers That Are Potentially Hormone Sensitive: the FUCHSia Study

Inclusion Criteria: * Written informed consent prior admission to the study * Age ≥ 18 years at the moment of signing the informed consent * Recurrent or metastatic low grade uterine sarcomas (low grade endometrial stromal sarcoma, low grade adenosarcoma without sarcomatous overgrowth and low grade leiomyosarcoma), low-grade endometrial carcinomas, sex cord stromal tumors (granulosa cell tumors...) and low grade serous ovarian cancer * Measurable disease, according to RECIST v1.1 criteria, assessed by CT scans * ER-positive tumors based on immunohistochemistry, assessed using the Allred scoring system (based on intensity and percentage of positive cells, see Appendix 4), and archival tissue available * At least and maximum of 1 prior line of hormonal therapy (tamoxifen, progestins and/or aromatase inhibitors). Response on 1st line hormonal therapy must have lasted for at least 3 months. * Eastern Cooperative Oncology Group (ECOG) performance status: 0-2 * Demonstrate adequate organ function: platelets \> 100 x 10E9/L, serum total bilirubin \< 1.5x Upper Limit of Normal (ULN) (patients with confirmed Gilbert's syndrome may be included in the study), alanine transaminase or aspartate transaminase \< 2.5x ULN if no demonstrable liver metastases or \< 5x ULN in presence of liver metastases * Post-menopausal status as defined by (i) age 60 or more, or (ii) age 45-59 and satisfying the following criteria: amenorrhea for at least 12 months and FSH in postmenopausal range, or (iii) …