Abstract PD15-06: PD15-06 Pathologic complete response and breast-conserving surgery are associated with improved prognosis in patients with early-stage triple-negative breast cancer treated with neoadjuvant chemotherapy

Abstract Background: Neoadjuvant chemotherapy (NACT) is standard of care for patients with triple-negative breast cancer (TNBC). Treatment response, especially pathologic complete response (pCR), is a strong predictive factor for treatment outcome. In the setting of up-front surgery, retrospective data have suggested improved outcome in patients with early TNBC that received breast-conserving surgery with adjuvant radiotherapy (BCT) as compared to mastectomy. Methods: We identified 2632 patients with early TNBC from the German Breast Group meta-database. Patients with cT1-2 cN0 and ypN0, available surgery and follow-up data were eligible for this project. A total of 1074 patients from 8 prospective NACT trials were analyzed. Endpoints of interest were locoregional recurrence as first site of relapse (LRR, other sites of recurrence were considered competing events), disease-free survival (DFS) and overall survival (OS); analyses were performed using univariate and multivariate Fine-Gray (for LRR) and Cox models including study, age, cT, surgery type and pCR. For the analyses including pCR as covariable, only patients at risk at the landmark time were evaluated. Results: Median age was 48 years, 69.6% of patients had cT2 tumors and 85.3% underwent BCS. Of the 1074 analyzed patients, 48.8% achieved pCR. After a median follow-up of 64 months, there were 94 (8.8%) locoregional events as first site of relapse. Upon univariate analysis, absence of pCR (hazard ratio [HR]=2.28; 95%CI 1.44-3.61; p< 0.001) and ypT-stage (ypT0/is vs. ypT1-3, HR=0.61; 95%CI 0.40-0.95; p=0.028) were significantly associated with LRR, while type of surgery, age and cT-stage were not. Upon multivariate analysis, absence of pCR was the only factor associated with increased risk of LRR (HR=2.22; 95%CI 1.38-3.58; p=0.001). Patients that underwent mastectomy (N=158) were significantly younger (age ≤ 50 years 72.8% vs. 59.9% for BCT [N=916]; p=0.002) DFS and OS was significantly better in patients who underwent BCT compared to mastectomy (DFS: HR=0.47; 95%CI 0.34-0.66; p< 0.001 and OS: HR=0.40; 95%CI 0.26-0.63; p< 0.001). In multivariate analysis, BCT was associated with a significantly better DFS and OS as compared to mastectomy (DFS: HR=0.51; 95%CI 0.36-0.72; p< 0.001; and OS HR=0.43; 95%CI 0.27-0.68; p< 0.001), whereas absence of pCR was associated with significantly worse DFS and OS (DFS: HR=2.43; 95%CI 1.78-3.31; p< 0.001; and OS: HR=3.15; 95%CI 1.94-5.10; p< 0.001). Conclusions: In this retrospective analysis from the GBG meta-database, treatment response, e.g. pCR, was the main determinant of locoregional recurrence in patients with early stage TNBC treated with NACT. BCT was associated with improved DFS and OS compared to mastectomy, which may at least in part reflect favorable patient selection. Citation Format: David Krug, Valentina Vladimirova, Michael Untch, Thorsten Kühn, Andreas Schneeweiss, Carsten Denkert, Beyhan Ataseven, Christine Solbach, Bernd Gerber, Hans Tesch, Michael Golatta, Sabine Seiler, Jörg Heil, Valentina Nekljudova, Sibylle Loibl. PD15-06 Pathologic complete response and breast-conserving surgery are associated with improved prognosis in patients with early-stage triple-negative breast cancer treated with neoadjuvant chemotherapy [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD15-06.