P–446 Controlled ovarian stimulation protocols for oocyte vitrification induce differential gene expression profiles in primary tumours of breast cancer

Abstract Study question Could controlled ovarian stimulation (COS) protocols used in fertility preservation (FP) impact on malignant cell proliferation and tumour molecular profiling of breast cancer (BC) patients? Summary answer Letrozole supplementation during ovarian stimulation for oocyte vitrification could be considered as a safe procedure in estrogen-dependent BC patients undergoing FP. What is known already High estradiol levels associated to COS could promote changes in gene expression in estrogen-positive BC tumors. Estradiol levels reached during the ovarian stimulation could aggressively promote malignant cell proliferation and cell migration to adjacent organs. Aromatase inhibi…