Abstract PS5-03-07: A Real-World Study on the Current Status of First-Line Treatment and Clinical Outcomes in Patients with Advanced Triple-Negative Breast Cancer (aTNBC) in Western China

Abstract Background: Triple-negative breast cancer (TNBC) is characterized by limited treatment options and poor prognosis, with chemotherapy serving as the primary treatment approach. Immunotherapy and targeted therapy have become critical strategies for improving prognosis in patients with TNBC, but real-world adoption remains unclear. This study aimed to characterize first-line (1L) treatment and clinical outcomes in patients with advanced TNBC (aTNBC) in Western China. Methods: This retrospective study enrolled aTNBC patients initiating first-line therapy (2018-2023) in West China Hospital. Descriptive statistics summarized treatment adoption and patient characteristics.The primary endpoint was overall survival (OS), progression-free survival (PFS), and time to next treatment or death (TTNTD). Results: A total of 282 patients with aTNBC were included, with a median age of 51 years (range, 22-80). The mOS was 22.0 months(95% CI, 19.6-25.1), mPFS was 7.8 months(95% CI, 7.1-9.0) and mTTNTD was 8.3 months(95% CI, 7.2-9.4) among patients. Patients aged 40-65 years had significantly longer OS (p=0.04). Patients with recurrent metastatic TNBC demonstrated significantly prolonged PFS (p=0.04) and TTNTD (p=0.04) compared to those with de novo metastatic TNBC; however, no statistically significant difference in OS was observed. Patients with a treatment-free interval (TFI) exceeding 12 months demonstrated significantly longer OS (p<0.001). Ipsilateral chest metastasis was associated with shorter OS(p=0.005), while primary breast recurrence correlated with reduced PFS (p=0.02) and TTNTD (p=0.02) in locoregional recurrence patients. Patients who developed distant metastasis exhibited significantly shorter OS (p=0.04), PFS (p=0.002), and TTNTD (p=0.002); notably, those with liver or lung metastasis as the first metastatic site showed particularly poor prognosis (liver PFS (p<0.001) and TTNTD (p=0.002); lung OS (p=0.02), PFS (p=0.003) and TTNTD (p<0.001)). PD-L1 testing (22C3 assay) was performed in 20.6% (58/282) of patients, yielding a 50.0% positivity rate (29/58, CPS ≥1), among whom 8 received immune checkpoint inhibitors (ICIs) in 1L treatment. 17 patients received ICIs without established PD-L1 biomarker eligibility (either PD-L1-negative or untested status). Pathogenic germline BRCA1/2 mutations were identified in 19 of 83 tested patients (22.9%), among whom only 5 received PARP inhibitor in 1L treatment. Additionally, ADC-based therapy was administered to 9 patients in the 1L treatment. Conclusions: In Western China, 1L treatment for aTNBC predominantly relies on chemotherapy with limited ICI and targeted therapy due to economic and logistical barriers. Future expanding access to immunotherapy and targeted therapy in Western China is clinically imperative to address current care disparities. Citation Format: T. Luo, C. Zhuang, Y. Song, P. He, D. Zheng, X. Yan, X. Zhong, T. Tian, B. Wei, Y. Xie, J. Chen, Q. Lv. A Real-World Study on the Current Status of First-Line Treatment and Clinical Outcomes in Patients with Advanced Triple-Negative Breast Cancer (aTNBC) in Western China [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 PS5-03-07.