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

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 ( = 7, 9.2%) or cryopreserved material ( = 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 (InCA), InCA-SHS, grant no. 2016-124, and is part of the Young Breast Cancer Project, funded by Monoprix.