Abstract PS4-08-20: Immune-related adverse events and pathological complete response in early TNBC treated with neoadjuvant chemo-immunotherapy: a real-world analysis

Abstract Introduction: Triple-negative breast cancer (TNBC) is the most aggressive breast cancer subtype. After the KEYNOTE-522 trial showed improved pathological complete response (pCR) rates, neoadjuvant chemo-immunotherapy (Ch-IT) became standard of care. This study evaluates the efficacy and safety of Ch-IT in early-stage TNBC, focusing on the association between irAEs and pCR. Methods:We conducted a retrospective analysis of medical records from 68 patients with early-stage TNBC 2 cm and/or lymph node positive who received neoadjuvant Ch-IT between January 2023 and November 2024. Endpoints were the rate of pCR (defined as absence of invasive cells in breast and lymph nodes), rate of treatment discontinuation prior to surgery, incidence of irAEs (graded according to CTCAE v5.0) and their association with pCR. Results: A pCR was achieved in 44 patients (64.7%). Baseline clinical and pathological characteristics stratified by pCR status are shown in Table 1. Neoadjuvant treatment was permanently discontinued before surgery in 15 patients (22.1%) all attributable to Ch-IT toxicity. A total of 32 patients (47.1%) experienced irAEs detailed in Table 2. No statistically significant association was observed between the occurrence of irAEs and achieving a pCR (χ2 = 1.36; p = 0.24); however, 5 of the 6 patients who developed grade ≥3 irAEs achieved a pCR. Conclusions: In this real-world cohort of patients with early-stage TNBC, neoadjuvant Ch-IT demonstrated a pCR rate consistent with the KEYNOTE-522 trial. Although no statistically significant association was found between irAEs and pCR, a numerical trend was observed, particularly among patients with grade ≥3 events. Further studies with larger cohorts are warranted to elucidate the potential predictive role of irAEs in treatment response and long-term outcomes. Table 1 Table 2 Citation Format: G. Lendinez-Sanchez, A. Godoy-Ortiz, N. Bousdar-Ahmed, P. Vazquez-Rojas, B. Villaescusa-González, A. Romanos-Nanclares, J. Pascual, F. Carabantes, E. Alba, E. Villar-Chamorro, N. Ribelles, A. Sánchez-Munoz. Immune-related adverse events and pathological complete response in early TNBC treated with neoadjuvant chemo-immunotherapy: a real-world analysis 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 PS4-08-20.