Abstract RF2-03: Adjuvant epirubicin plus cyclophosphamide followed by taxanes with or without carboplatin for early stage triple-negative breast cancer (RJBC 1501): a randomized controlled phase III trial

Abstract Background: RJBC 1501 (NCT02455141) is a prospective phase III study to compare the efficacy and safety of adjuvant epirubicin plus cyclophosphamide (EC) followed by taxanes (T) versus same regimen plus carboplatin (EC-TCb) in early-stage triple negative breast cancer (TNBC). Methods: Patients with node positive or node negative (with tumor size ≥1.0cm) TNBC who received definitive surgery were randomized 1:1 to receive EC-T or EC-TCb. Taxanes consisted of either weekly paclitaxel for 12 doses or docetaxel every 3 weeks for 4 cycles. Carboplatin was given weekly (AUC 2) for 12 doses or every 3 weeks (AUC 5-6) for 4 cycles, concurrent with taxanes. The primary endpoint was disease-free survival (DFS) in the intention-to-treat (ITT) population. Secondary endpoint includes distant DFS (DDFS), overall survival (OS), and safety. Results: Between March 2016 and March 2023, 786 patients were randomized (EC-T: n = 391; EC-TCb: n = 395). Baseline characteristics were balanced: median age ≤50 years (49.6%), T1 stage (46.6%), node-negative (72.3%). A majority of patients (76.5%) received 3-weekly docetaxel. After a median follow up of 4.52 (IQR 2.83 to 6.06) years, 103 events were reported: 62 in the EC-T group and 41 in the EC-TCb group. Addition of carboplatin significantly improved DFS (hazard ratio HR, 0.66; 95% CI, 0.44 to 0.97, P = 0.034), with 3-year DFS of 89.8% (95%CI 86.8 to 92.9%) for EC-T and 93.1% (95%CI 90.5 to 95.7%) for EC-TCb. EC-TCb regimen was also associated with a superior DDFS (HR, 0.61; 95% CI, 0.38 to 0.98, P = 0.040) and OS (HR, 0.39; 95% CI 0.16 to 0.94, P = 0.029) compared to EC-T treatment. Grade 3-4 adverse events were more frequent among EC-TCb arm (49.9%) than EC-T arm (38.7%), primarily driven by higher rates of neutropenia (47.0% vs 37.8%) and thrombocytopenia (4.5% vs 0%). Other grade 3-4 toxicities were comparable between groups. Conclusion: Adding carboplatin to adjuvant EC-T chemotherapy significantly improves DFS, DDFS, and OS in patients with early-stage TNBC. While additional carboplatin treatment was associated with increased hematologic toxicity, no new safety signals emerged. Citation Format: X. Chen, J. Huang, H. Shi, J. Zhu, W. Wu, G. Ye, Q. He, Y. Shi, A. Zhang, X. Xie, X. Wang, X. Chen, W. Wu, J. Wu, Z. Li, Z. Li, Y. Dai, W. Ren, Q. Shao, Y. Chen, Y. Zeng, M. Pegram, K. Shen. Adjuvant epirubicin plus cyclophosphamide followed by taxanes with or without carboplatin for early stage triple-negative breast cancer (RJBC 1501): a randomized controlled phase III trial 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 RF2-03.