Abstract PS4-10-24: Longitudinal trends in prognosis and post-treatment pregnancy in young woman with triple-negative breast cancer

Abstract Background: Triple-negative breast cancer (TNBC) in young women has traditionally been associated with poor prognosis. However, treatment outcomes are expected to improve with advances such as response-guided neoadjuvant chemotherapy, PARP inhibitors, and immune checkpoint inhibitors. For young women who have a desire for future pregnancies, whether pregnancy and childbirth are feasible after breast cancer treatment is a critical concern. Therefore, fertility preservation (FP) before cancer treatment and shared decision-making regarding post-treatment pregnancy are essential. Objective: To investigate treatment outcomes, temporal trends in FP, and pregnancy outcomes among young patients with TNBC. Methods: A retrospective analysis was conducted on 179 young patients under the age of 40 with stage I-III TNBC who underwent curative surgery at our institution between 2007 and 2022. We investigated treatment outcomes, FP rates, and subsequent pregnancy status. The primary endpoints were breast cancer recurrence, the development of secondary malignancies, and overall survival. Secondary endpoints were pregnancy and childbirth after breast cancer treatment. Results: The mean age at surgery was 34.4 years. Eighty-three patients (46.4%) had a history of childbirth. Among those tested, 41 patients (43.2%) carried pathogenic BRCA1/2 variants. The stage distribution was stage I in 42 patients (23.5%), stage II in 103 (57.5%), and stage III in 34 (18.0%). Chemotherapy was administered to 171 patients (95.5%), of whom 93 (52.0%) received neoadjuvant therapy. With a median follow-up of 5.8 years (range: 0.1-17.5), recurrence including contralateral breast cancer occurred in 14 patients (7.8%), secondary malignancies in 5 (2.8%)—of whom 3 had ovarian cancer—and 25 patients (14.0%) died. At the time of diagnosis, 61 patients (34.1%) had desire for future pregnancy. Among them, 26 (14.5%) underwent FP before chemotherapy, and 22 (12.3%) received LHRH analogs during chemotherapy for ovarian function protection. Comparing two time periods, 2007-2014 and 2015-2022, the 5-year overall survival significantly improved from 78.7% to 94.5% (p = 0.0088). FP implementation also increased over time, with the FP rate among those with desire for future pregnancies at the time of diagnosis rising from 12% to 58.3%. Seventeen patients conceived after treatment (6 spontaneously, 9 with assisted reproductive technology, 2 unknown), resulting in 23 pregnancies and 17 live births in 15 patients (8.4% of the total cohort, 24.6% of those who had desire for future pregnancies at the time of diagnosis). Among the patients who gave birth, one had been treated with immune checkpoint inhibitors. No serious perinatal complications were observed. All patients were disease-free at the time of attempting conception. No distant recurrence or breast cancer-related deaths occurred after childbirth. To date, none of the patients who treated with PARP inhibitor therapy became pregnant. Conclusion: Although numbers are limited, young patients with TNBC who attempted pregnancy after completing standard systemic therapy had favorable oncologic and perinatal outcomes. In this study, the treatment outcomes and FP implementation rate for young patients with TNBC improved over time. This real-world data may be useful in supporting shared decision-making for reproductive planning and treatment decisions for young patients with TNBC. Citation Format: M. Kasahara, A. Kataoka, A. Kanazawa, Y. Ito, Y. Kimura, N. Yoshida, U. Nakadaira, N. Uehiro, C. Takahata, Y. Ozaki, M. Nishimura, T. Takano, T. Kogawa, T. Sakai, T. Ueno. Longitudinal trends in prognosis and post-treatment pregnancy in young woman with triple-negative breast cancer [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS4-10-24.