Abstract PS4-08-14: A Systematic Review and Extracted Individual Patient Data Meta-analysis of Long- Term Outcomes in Triple-Negative Breast Cancer after a Pathologic Complete Response: Does the Type of Neoadjuvant Therapy Matter?

Abstract INTRODUCTION: Neoadjuvant chemotherapy is standard of care for stage IB-III triple-negative breast cancer (TNBC), with pathological complete response (pCR) strongly associated with survival. Although the escalation of neoadjuvant therapies with platinum and immune checkpoint inhibitors (ICI) improves pCR rates and long-term outcomes, patients with pCR in the control arms of pivotal trials also show favorable outcomes. Whether the type of neoadjuvant regimen leading to pCR impacts long-term survival differently is largely unknown. Methods: We conducted a systematic review and meta-analysis, searching PubMed, Embase, Cochrane, and conference proceedings for phase II and III trials including patients with early-stage TNBC and pCR. A pooled analysis of Kaplan-Meier-derived individual patient data was performed for event-free survival (EFS) and overall survival (OS), with subgroup analyses by treatment regimens. Results: Of 2,830 identified publications, 18 trials (16 randomized and 2 single-arm) comprising 3,430 TNBC patients with pCR were included. Neoadjuvant ICI with chemotherapy improved EFS (HR 0.67; 95%CI 0.50-0.89; p<0.01) compared with chemotherapy-only regimens, with no significant OS difference for patients with pCR (HR 0.84; 95%CI 0.50-1.41; p=0.51). In contrast, EFS and OS were not significantly different regardless of platinum use (HR 0.55; 95%CI 0.20-1.50; p=0.24 and HR 0.33; 95%CI 0.09-1.22; p=0.10, respectively). Similarly, anthracycline-containing regimens showed comparable EFS to anthracycline-free regimens (HR 0.86; 95%CI 0.51-1.45; p=0.58). For patients with pCR after ICI therapy, the benefit of adjuvant ICI for EFS or OS was not statistically significant (HR 1.16; 95%CI 0.55-2.44; p=0.70 and HR 2.91; 95%CI 0.40-21.37; p=0.29, respectively). No significant EFS difference was observed between neoadjuvant strategies using 6 or 8 chemotherapy cycles (HR 0.87; 95% CI 0.49-1.55; p=0.64). Conclusion: Neoadjuvant ICI-based regimens improve EFS in patients with early-stage TNBC beyond pCR. However, among patients who achieved pCR, EFS seems not to be impacted by the type of neoadjuvant chemotherapy used. Citation Format: L. Ravani, S. Wander, M. Kok, K. McCann, J. Cortes, R. Barroso-Sousa, M. Lustberg, J. Binez, I. Michelon, L. Testa, M. Wang, D. Deng, R. Colombo Bonadio. A Systematic Review and Extracted Individual Patient Data Meta-analysis of Long- Term Outcomes in Triple-Negative Breast Cancer after a Pathologic Complete Response: Does the Type of Neoadjuvant Therapy Matter? [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 PS4-08-14.