Abstract PO2-11-05: Pregnancy Trends Following Breast Cancer Treatment: Insights from a Large Single-Center Experience
Authors: Lee Young-jin , Yoo Tae-Kyung , Lee Sae Byul , Kim Jisun , Chung Il-Yong , Ko Beom Seok , Lee Jong Won , Son Byung Ho , Kim Hee Jeong , Ahn Jeonghee , Kim Seonok 
Published: May 2024

Abstract
Background
The treatment of breast cancer (BC), particularly chemotherapy and long-term endocrine therapy (ETx), can have an impact on fertility which young women with BC have concerns about. This study was therefore conducted with the objective of providing comprehensive real-world data on pregnancy following BC treatment, aiming to shed light on this crucial aspect of survivorship and potentially guide clinical practice and patient counseling.
Methods
A retrospective analysis was conducted using medical records of women aged 18-40 years diagnosed with BC at a single tertiary medical center between December 2010 and September 2020. The pregnancy rate and timing in relation to characteristics and treatment were analyzed, along with the outcomes of discontinuing ETx for the purpose of pregnancy. Statistical analyses including Kaplan-Meier curves and Cox regression were performed.
Results
The study included 995 patients, with a mean age at diagnosis of 31.5 years. Of these, 115 (11.6%) patients became pregnant after BC treatment. Patients with a prior history of pregnancy had a lower likelihood of conception post-treatment (HR=0.39, 95% CI: 0.24-0.67, P&lt; 0.001). Women with hormone receptor positive BC was also associated with lower pregnancy rates than with hormone receptor negative BC (HR=0.52, 95% CI: 0.36-0.77, P=0.001). Age at diagnosis and chemotherapy did not significantly impact pregnancy rates (P=0.251 and P=0.140, respectively). Among 662 women with hormone receptor positive BC, there were 76 (11.5%) women who discontinued ETx for the purpose of pregnancy and 69.7% (53 out of 76) achieved pregnancies. The median duration of medication before cessation among these women was 26.5 months and the duration of ETx did not significantly affect pregnancy rates (P=0.204). Recurrence after discontinuation of ETx for pregnancy was observed in 17% (13 out of 76) of cases. The median breast cancer-free interval among these cohort was 71 months. Late recurrence, occurring after 5 years of treatment, was observed in 77% (10 out of 13) of cases. Among the patients who experienced recurrence, 62% (8 out of 13) were loco-regional, while 38% (5 out of 13) were distant recurrences and the success rate of achieving pregnancy was 69% (9 out of 13), while 31% (4 out of 13) did not get pregnant.
Conclusion
This study provided real-world data regarding the influence and outcomes of ETx on pregnancy in young BC survivors. The discontinuation of ETx for the purpose of pregnancy appears to result in successful conception. Recurrence rates after therapy discontinuation for pregnancy were observed in a subset of cases, with late and loco-regional recurrences being more common.
Results of uni- and multi-variable cox proportional hazards model evaluating time to pregnancy
* The pregnancy rate was calculated using Kaplan-Meier (KM) estimates.
Pregnancy rate according to ETx and its discontinuation
Pregnancy rate according to duration of ETx prior to Discontinuation for pregnancy
* The p-value was calculated using Chi-square analysis
Citation Format: Young-jin Lee, Tae-Kyung Yoo, Sae Byul Lee, Jisun Kim, Il-Yong Chung, Beom Seok Ko, Jong Won Lee, Byung Ho Son, Hee Jeong Kim, Jeonghee Ahn, Seonok Kim. Pregnancy Trends Following Breast Cancer Treatment: Insights from a Large Single-Center Experience [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-11-05.