Abstract GS3-09: Chances of pregnancy after breast cancer, reproductive and disease outcomes: A systematic review and meta-analysis

Background: Pregnancy-related issues are a priority for young breast cancer (BC) patients. Increasing evidence has shown that pregnancy after prior BC diagnosis is feasible. Nevertheless, few BC survivors conceive following anticancer treatment completion and many physicians remain concerned about the potentially detrimental effects of pregnancy after BC in terms of fetal/obstetrical outcomes and maternal prognosis. This systematic review and meta-analysis aims at providing updated and solid evidence on these important issues. Methods: A systematic literature review up to January 31, 2020 with no language restriction was conducted to identify studies including patients with a pregnancy after prior BC diagnosis. Chances of pregnancy after BC, fetal and obstetrical outcomes, disease-free survival (DFS) and overall survival (OS) were assessed. Pooled relative risks (RRs), hazard ratios (HRs) or odds ratio (ORs) with 95% confidence intervals (CI) were calculated using the random effects models. The study is registered with the PROSPERO registration number CRD42020158324. Results: Overall, 39 studies were included. Out of the 8,265,713 young women included in these studies, 8,093,401 were from the general population, 57,739 had cancers other than BC, 114,573 had BC. Among the 114,573 BC patients, 7,505 had a pregnancy after BC diagnosis and 107,068 did not. Compared to women from the general population, BC patients had 60% reduced chances of having a pregnancy following anticancer treatment completion (RR 0.40, 95% CI 0.32-0.49). Among other cancer patients, only women with prior cervical cancer had lower pregnancy rates (RR 0.33, 95% CI 0.31-0.35) than BC patients. Compared to the general population, BC survivors had significantly increased risks of low birth weight (OR 1.50, 95% CI 1.31-1.73), small for gestational age (OR 1.16, 95% CI 1.01-1.33), preterm delivery (OR 1.45, 95% CI 1.11-1.88) and caesarean section (OR 1.14, 95% CI 1.04-1.25). No significant increased risk of congenital abnormalities (OR 1.63, 95% CI 0.89-2.98) or other pregnancy or delivery complications (spontaneous or induced abortion, gestosis, antepartum or postpartum hemorrhage) was observed. Prior chemotherapy exposure or short pregnancy interval (defined as Pregnancy after BC was not associated with a negative impact on patients’ outcomes. Compared to BC patients without subsequent pregnancy, those with pregnancy after BC had better OS (HR 0.56, 95% CI 0.46-0.67) and DFS (HR 0.73, 95% CI 0.56-0.94). Similar results were observed in the studies correcting for the potential “healthy mother effect” (OS: HR 0.52, 95% CI 0.42-0.65; DFS: HR 0.74, 95% CI 0.58-0.96). No detrimental prognostic effect of pregnancy after BC was observed in patients with hormone-receptor positive disease (DFS: HR 1.10, 95% CI 0.73-1.66), while better outcomes were observed for those with hormone-receptor negative disease (DFS: HR 0.72, 95% CI 0.55-0.95). The safety of pregnancy after BC was observed irrespective of BRCA status, nodal status, previous chemotherapy exposure, pregnancy interval and pregnancy outcomes. Conclusions: This large meta-analysis provides solid evidence on the safety of pregnancy after prior BC diagnosis. The increased risk of fetal and obstetrical complications (but not of congenital abnormalities) calls for ensuring a closer monitoring of these pregnancies. The significantly reduced chances of conceiving as compared to the general population and other cancer patients should raise further awareness on the need to improve the oncofertility counseling of young BC patients wishing to complete their family planning following anticancer treatment completion. Citation Format: Eva Blondeaux, Marta Perachino, Marco Bruzzone, Richard A. Anderson, Evandro De Azambuja, Philip D. Poorvu, Hee Jeong Kim, Cynthia Villarreal-Garza, Barbara Pistilli, Ines Vaz-Luis, Cristina Saura, Kathryn J. Ruddy, Maria Alice Franzoi, Chiara Sertoli, Marcello Ceppi, Hatem A. Azim, Jr., Frederic Amant, Isabelle Demeestere, Lucia Del Mastro, Ann H. Partridge, Olivia Pagani, Fedro A. Peccatori, Matteo Lambertini. Chances of pregnancy after breast cancer, reproductive and disease outcomes: A systematic review and meta-analysis [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr GS3-09.