Time-to-pregnancy in patients with previous breast cancer and unexposed women: a prospective exposed-unexposed cohort study

Abstract

Background: Data on fertility after breast cancer (BC) relative to the general population are lacking. This study aimed to compare the time-to-pregnancy between women with and without prior BC seeking to become pregnant. Methods: We conducted a prospective exposed-unexposed cohort study between March 13, 2018 and June 27, 2019, recruiting participants via the collaborative network Seintinelles. Women aged 18–43 years with a history of localized BC without relapse (exposed) were compared to women without BC (unexposed). Follow-up data were collected every six months over three years. The primary endpoint, time-to-pregnancy, was analyzed using Kaplan–Meier survival analysis with inverse probability weighting. Censoring was performed if women stopped trying to conceive for personal reasons, were lost to follow-up before conception, or completed the study without achieving pregnancy or using assisted reproductive technologies (ART). Findings: Among 4351 women enrolled, 642 sought pregnancy during the study period (76 exposed, 566 unexposed). Among them, 50 exposed (65.8%) and 402 weighted unexposed women (weighted percentage 71.0%) became pregnant at least once. Median time-to-pregnancy was 5.0 months, 95% CI [3.0–7.0] for exposed and 3.0 months, 95% CI [2.0–5.0] for unexposed women (difference in median time-to-pregnancy: 2.0 months, 95% CI [−2.5; 5]). Two years after starting to seek pregnancy, 74.9% of weighted unexposed women and 74.1% of exposed women obtained a pregnancy. Overall, 15 exposed women (19.8%) used either ART methods (n = 7, 9.2%) or cryopreserved material (n = 8, 10.5%) and 25 unexposed women (4.4%) used ART. The median time-to-pregnancy was 3.0 months for both exposed and unexposed women (95% CI [2.0; 5.0] and [2.0; 4.0] respectively) (difference in median time-to-pregnancy: −0.0 months [−2.0; 3.0]) in women who sought pregnancy spontaneously, and 14.0 months for exposed (95% CI [6.0–27.0]) and 17.6 months for unexposed women (95% CI [17.6–30.0]) in women seeking pregnancy with ART. Interpretation: In this study from a French collaborative research network, we found no strong evidence of a largely reduced time-to-pregnancy in exposed women seeking to become pregnant compared with unexposed women. Further research on fertility outcomes in the broader population of BC survivors is warranted. Funding: The FEERIC study was funded by Institut National du Cancer (InCA), InCA-SHS, grant no. 2016-124, and is part of the Young Breast Cancer Project, funded by Monoprix.