Fertility outcomes several years after urgent fertility preservation for breast cancer patients

Objective To study the fertility outcomes of women who tried to conceive after breast cancer treatment and fertility preservation. Design Retrospective observational, bicentric cohort study. Subjects and Exposure All patients who had undergone fertility preservation before breast cancer treatment between January 2013, and July 2019 were included (n=844). The end-point date was March 1, 2022. Patients with missing data on pregnancy attempts after cancer diagnosis (n=195) were excluded from the pregnancy analysis. Main outcome measures Cumulative incidences of pregnancy and live birth were calculated. For women who became pregnant, the time to conception was calculated between the first fertility preservation consultation and the estimated day of conception. For those who did not conceive, we considered the time between first fertility preservation consultation and the end-point date or the date of patient death. A Cox regression model was used to study the predictive factors of pregnancy and live birth. Results Among the 649 patients with available data on pregnancy attempts after breast cancer diagnosis, 255 (39.3% [35.5-43.2]) tried to conceive (median follow-up 6.5 years). Overall, 135 (52.9% [46.6-59.2]) of these patients achieved a pregnancy, mainly through unassisted conception (79.3% [72.8-84.8]), and 99 reported a live birth (representing 38.8% of patients who attempted conception). In our cohort, 48 months after the first fertility preservation consultation, the cumulative incidence of pregnancy was 33.1% ([27.6-37.9]). After adjustment for age, parity, type of chemotherapy administration and endocrine therapy, only multiparity at diagnosis and absence of chemotherapy were positive predictive factors of pregnancy after cancer. Of the 793 patients who had vitrified oocytes/embryos, 68 used them (27% [21.3-32.5] of the patients who tried to conceive), resulting in 8 live births (11.8% [5.2-21.9]). Women who used their cryopreserved oocytes/embryos were older at the first consultation of fertility preservation (HR 1.71(1.42-2.21)), and chose more often to vitrify embryos (HR 1.76(1.28-2.23). Conclusion Although pregnancy rates after fertility preservation for breast cancer are low, most conceptions are achieved without medical assistance. Our findings provide useful information to advise women on the different techniques of fertility preservation, their efficacy and safety, as well as the relatively high chances of unassisted conception.