O-031 The italian multicenter study on oncofertility: pregnancy outcomes after oocyte thawing comparing different cancer types

Abstract Study question Does the type of tumour impact Fertility Preservation (FP) outcomes? Data from an Italian multicenter study conducted by the Italian Assisted Reproductive Technology Registry (IARTR) Summary answer Despite the higher age, breast cancer patients have higher pregnancy rates than haematological cancer patients in IVF cycles with thawed oocytes. What is known already Most studies on fertility preservation in young female cancer patients didn’t shown statistically significant differences in ovarian reserve and in the outcome of controlled ovarian stimulation compared to the control group. The control group often consists of non-oncologic infertile patients undergoing oocyte vitrification for assisted reproductive techniques. Only few studies have separately analysed the impact of cancer type on ovarian stimulation outcomes. Moreover, it is not always possible to evaluate pregnancy outcomes due to the limited number of published studies and to the fact that many cancer patients often achieve spontaneous pregnancies without the use of cryopreserved oocyte. Study design, size, duration This multicenter study was conducted by the IARTR in collaboration with seven ART centers participating in the PreFerIta project, the first Italian registry on FP. The study aims to compare, across different cancer diagnoses, the outcomes of oocyte thawing cycles for fertility preservation performed between 2014 and 2023. Participants/materials, setting, methods A total of 201 cancer patients underwent 277 oocyte thawing procedures during the study period. Baseline characteristics, embryo transfer details, and outcomes were compared across four main groups: breast cancer, haematological cancers, ovarian cancer, and other solid cancers. Subgroup analyses were also conducted based on the type of embryo transferred (fresh vs. frozen). The primary outcome was the clinical pregnancy rate. Statistical analyses were performed using the Kruskal–Wallis test and the Chi-square test as appropriate. Main results and the role of chance The primary cancer diagnosis was breast cancer (121 patients, 60.2%), followed by haematological cancers (48 patients, 23.9%), other solid cancers (20 patients, 9.9%), and ovarian cancer (12 patients, 6.0%). Patients with breast and other cancers were older at the time of oocyte cryopreservation and thawing, with a higher mean number of thawed oocytes. Haematological cancer patients had a longer duration of cryopreservation and more thawing cycles. The return rates were lower in patients with other cancers. Across the groups, similar outcomes were observed for the number of frozen oocytes, oocyte survival, fertilization rates, transferred embryos, and frozen embryo transfer rates. Following 268 embryo transfers, 71 clinical pregnancies were achieved, including 7 twin pregnancies, resulting in 44 deliveries and 50 live births. Clinical pregnancy rates were higher in breast cancer patients compared to haematological cancers, both per patient (43.0% vs. 20.8%) and per transfer (32.3% vs. 13.9%), with no significant differences in live birth rates per patient. Subgroup analysis revealed a higher mean number of embryos transferred in fresh cycles, except in ovarian cancer. Transfers with thawed embryos showed superior clinical pregnancy (66.7%) and live birth rates (44.4%) compared to fresh embryo transfers (25.4% and 16.4%, respectively) only in breast cancer. Limitations, reasons for caution The retrospective nature of the study and the fact that ovarian stimulation protocols can differ between Centers. In the breast cancer patient group, no distinction was made regarding the presence of BRCA gene mutations. The sample size is small because many patients did not return for oocyte thawing. Wider implications of the findings This is the largest Italian multicentre study on FP, correlating cancer type with ovarian stimulation response, thereby to help cancer patient’s management and develop more precise fertility treatment protocols. Trial registration number No