Fertility Preservation for Patients With Breast Cancer: Altered Response to Ovarian Stimulation and Loss of Cholesterol Homeostasis in Ovarian Follicles

Advances in cancer diagnosis and treatments have improved the 5-year survival rate for patients over the last decade. Nevertheless, cancer treatments frequently alter patient's fertility, thus compromising their ability to conceive a child after remission. Consequently, it is recommended to propose fertility preservation to patients before cancer therapy. The reference technique for preserving women's fertility the vitrification of mature oocytes after hormonal stimulation. In the context of cancer, different studies have shown that ovarian response to stimulation seems to be altered compared to healthy context, with a reduced number of mature oocytes collected, and altered oocyte quality, thus reducing the number of oocytes capable of producing a viable embryo. Hence, cancer seems to exert a deleterious impact on women's fertility. Nevertheless, the mechanisms by which the cancer may impair the ovarian functions are poorly understood. This innovative project aims to study the impact of breast cancer itself (the most frequent cancer in reproductive-aged women) on ovarian functions, and more precisely on the cholesterol biosynthesis pathway. Indeed, cholesterol homeostasis is essential for oocyte maturation and fertilization. The objectives of this study are i) to evaluate the impact of breast cancer on ovarian reserve and response to hormonal stimulation according to the molecular subtypes of breast cancer and ii) to evaluate the impact of breast cancer on ovarian cholesterol homeostasis in granulosa cells and follicular fluids.

This original approach will improve the understanding of the mechanisms underlying the impact of breast cancer on ovarian functions, and will have a strong clinical impact by helping to optimize fertility preservation strategies based on tumour molecular subtypes.