Evaluation of Clinical Impact of Interruption VS Maintenance of AI in Patients With Locally Advanced/ Metastatic Low Grade Endometrial Stromal Sarcoma (LGESS)

Uterine sarcomas are rare tumors with an incidence of 1.7/100 000 women per year, including 20% of endometrial stromal sarcomas (ESS). Patients with low grade ESS (LGESS) have a good prognosis with a 5-year overall survival rates ranging from 66 to 98%, depending on the stage of the disease.

Majority of LGESS report estrogen receptor (ER) and/or progesterone receptor positive and a chromosomal translocation with JAZF1-SUZ12.

Based on the current European Society of Medical Oncology (ESMO)guidelines, the standard treatment for patients with early/non metastatic ESS is total hysterectomy plus or less bilateral salpingo-oophorectomy. The use of hormonal therapy (HT) for advanced or metastatic disease is recommended based on retrospective data from small series providing evidence that HT have an anti-tumor activity on LGESS. HT includes aromatase inhibitors (AI), progestins and gonadotrophin-releasing hormone.

Very few data are available in this rare disease, but retrospective analyses show that AI may provide response rates of 46 to 67% in metastatic LGESS patients (7% complete response, 60% partial response), with a mean duration of response of 24 months.

Even if AI are effective and well tolerated, chronical mild to moderate (grade 1-2) side-effects (arthritis, hot-flashes, osteoporosis, hypercholesterolemia, cardiac events) have a negative impact on patient's well-being because of the treatment long term duration and need to be balanced in such long term survival.

To date, the question of the optimal duration of HT in LGESS is still pending. The investigator propose an open-label, randomized, multicenter phase II study aiming at determining the feasibility of interruption of AI in patients with locally advanced or metastatic LGESS after long term stabilization or response to AI. The study will use a sequential bayesian design allowing for continuous monitoring of the main efficacy outcome, thus leading to a smaller more informative trial, and specifically tied to decision making. This design is particularly suited to characterize efficacy signals in the context of a very rare pathology. Moreover JAZF1-JJAZ1 fusion gene is not identified in all LGESS.

Ancillary studies will provide precious data aiming at:

* Identifying predictive factors of prolonged response to HT or late resistance (Next Generation Sequencing and Comparative Genome Hybridization). * Evaluating sociobehavioral (only for French sites) of patients by following questionnaire: Zimbardo Time Perspective Inventory (ZTPI) , Functional, Communicative and Critical Health Literacy/ 14-item Health Literacy Scale (FCCHL/HLS14), VICAN, Fear of Cancer Recurrence (FCR) and Patient-Generated Index (PGI).

• Overall survival [Срок оценки: From date of randomization to death due to any cause, assessed up to 60 months]
• Time to first subsequent chemotherapy/treatment or death [Срок оценки: From date of randomization to the earliest date of chemotherapy/treatment start date following study treatment discontinuation, or death due to any cause, whichever came first, assessed up to 60 months]
• Objective response rate after reintroduction of AI in the experimental arm [Срок оценки: From the date of AI reintroduction in the experimental arm to the date of subsequent progression or date of death due to any cause, whichever came first, assessed up to 60 months]
• Progression free survival after reintroduction of AI in the experimental arm [Срок оценки: From the date of AI reintroduction in the experimental arm to the date of subsequent progression or date of death due to any cause, whichever came first, assessed up to 60 months]
• Duration of response to AI after reintroduction [Срок оценки: From the date of first objective response following the reintroduction of AI to the date of the first subsequent documented radiological progression or death due to any cause, whichever came first, assessed up to 60 months]
• Incidence of Treatment-Emergent Adverse Events [Срок оценки: From date of randomization to follow-up visit Month 36 or death due to any cause, whichever came first, assessed up to 60 months]
• Quality of Life using European Organization for Research and Treatment of Cancer (EORTC) Quality of Life Questionnaire Core 30 (QLQ-C30) [Срок оценки: Every 6 months until the 36th month for each patient]