O-062 In vitro maturation of oocytes in connection with ovarian tissue cryopreservation

Abstract

Abstract Abstract text Discussing fertility preservation (FP) in young cancer patients has become a key component of routine oncological health care. Although ovarian stimulation followed by oocyte cryopreservation has been recommended in cases where two to three weeks are available before the start of chemotherapy, ovarian tissue cryopreservation (OTC) is the preferred option when this timeframe is not available and when the potential gonadotoxic impact of cancer therapy is deemed moderate or severe, or in prepubertal girls. During ovarian tissue processing in the laboratory, cumulus-oocyte complexes can be identified. In vitro maturation and further vitrification of oocytes retrieved in ex vivo from the extracted ovarian tissue (ovarian tissue oocytes in vitro maturation; OTO-IVM) can be attempted to enhance the future reproductive options of the patient. Although the number of reported live births after OTO-IVM are limited, this experimental FP procedure has potential to become a standard appended procedure in conjunction with OTC. In cancer patients with haematological tumours and ovarian invasion, or patients with primary tumours of the ovary, ovarian tissue grafting may be contraindicated because of the risk of reintroducing malignant cells. Utilisation of vitrified oocytes after OTO-IVM may be the only hope for genetic offspring for these patients. Moreover, exogenous hormonal pretreatment is not required and COC can be recovered during ovarian tissue processing in the majority of patients who undergo partial or total unilateral oophorectomy. Nevertheless, maturation rates after OTO-IVM vary and are generally lower compared to IVM of transvaginally harvested IVM oocytes; currently available IVM systems registered for clinical use will have to be adapted to accommodate the in vitro requirements of oocytes derived from extracorporeal ovarian tissue, and follow-up data are needed to assess the success rate and safety of this novel approach.