Patients enrolled in this study undergo standard or random start ovarian stimulation with Gonadotropins using antagonist protocol before the beginning of chemotherapy. Ovulation is triggered in all patients with a GnRH agonist since amendment P2015/091 (Decapeptyl 0,2mg).~At oocyte retrieval, aspirated follicular fluid is separated from the flush medium for hormonal assays, and oocytes are denuded for ICSI(Intra Cytoplasmic Sperm Injection) or vitrification. Cumulus cells are collected for subsequent analysis of oocyte quality gene expression.~A. Primary objective of the study is to evaluate efficiency of letrozole associated ovarian stimulation for fertility preservation in breast cancer patients in terms of oocyte maturation rate.~Patients' results for primary endpoint are prospectively compared to infertile patients undergoing COS without letrozole.~B. Secondary objectives of the study aim to evaluate safety of the protocol:~Estradiol and progesterone levels at ovulation triggering, ovulation and during luteal phase after oocyte retrieval (days 3 and 8)~The risk of disease relapse will be assessed by long-term follow-up of these patients (up to 5 years) as well as an evaluation of circulating tumoral DNA before and after ovarian stimulation.~Finally obstetrical outcomes will also be recorded.
The purpose of this study is to evaluate efficiency and safety of controlled ovarian stimulation (COS) associated with an aromatase inhibitor (letrozole) for fertility preservation in breast cancer patients.