O-194 Differences in long-term reproductive and oncologic outcomes of women with breast cancer undergoing fertility preservation with controlled ovarian stimulation versus without stimulation

Abstract

Abstract Study question What are the long-term outcomes after fertility preservation (FP) with versus without controlled ovarian stimulation (COS) in women with BC? Summary answer FP with COS was associated with higher rates of post-BC ART-treatment, while the rates of livebirth and all-cause mortality were similar between the two FP-groups. What is known already BC is the most common cancer in women of reproductive age, and the most common indication for female FP in Sweden. FP-methods including cryopreservation of oocytes, embryos and ovarian tissue are offered at Swedish academic centers within the health insurance coverage available to all citizens. A COS treatment is usually completed in 2-3 weeks, while ovarian tissue cryopreservation does not need COS and can be performed within a few days. To date, data on long term reproductive and oncologic outcome in women with BC undergoing FP with vs without COS are scarce. Study design, size, duration Multicenter nationwide cohort study aiming to investigate differences in long-term outcomes of women with BC receiving FP with or without COS at one of the seven regional FP programs in Sweden during 1994 - 2017 (N = 425). Participants/materials, setting, methods During the study period, 367 women received FP with COS (exposed) and 58 women underwent cryopreservation of ovarian tissue (unexposed) at Swedish centers. Reproductive outcomes, including post-diagnosis livebirths and the use of ART, as well as all-cause survival were investigated by linking of individuals in the cohort to several Swedish population-based registers. Outcomes among the women exposed and unexposed to COS were compared using Cox proportional hazard models adjusted for sociodemographic-, disease- and treatment characteristics. Main results and the role of chance Of 367 women exposed to FP with COS, 80 (22%) had at least one post-diagnosis livebirth (mean follow-up 4.3 years), compared to 17 (29%) of 58 women who underwent ovarian tissue cryopreservation (mean follow-up 5.9 years). Rates of ART-use during the follow-up were significantly higher in the group with COS (adjusted hazard ratio, aHR: 3.3, 95% CI:1.0-10.8), while livebirth rates (aHR: 1.1, 95% CI:0.6-2.0) as well as all-cause mortality rates (aHR:1.1, 95% CI:0.4-2.7) were similar between the groups. The five-years and ten-years cumulative incidence of post-BC livebirths was 18.3% and 41.4% among exposed to COS versus 23.7% and 38.9% among women with cryopreservation of ovarian tissue. Limitations, reasons for caution The FP programs in Sweden may differ from those in other countries, however data from population-based registers usually provide diversity. In Sweden, the use of gestational carriers is not permitted, thus individuals in this cohort had to achieve and carry by themselves the pregnancies resulting in post-BC livebirths. Wider implications of the findings The study results provide reassuring real-world reproductive and oncologic data following FP, both with and without COS, in women with BC. Our analyses are adjusted for identified confounders, and provide valuable information for FP-counselling of women with BC in need of FP. Trial registration number not applicable