Abstract PS4-10-17: The Impact of Pre-Treatment Clinical, Pathological, and Radiological Parameters on Pathological Complete Response and Prognosis Following Neoadjuvant Therapy in Patients with Triple-Negative Breast Cancer

Abstract Triple-negative breast cancer (TNBC), accounting for approximately 15% of all breast cancers, is a subtype characterized by the absence of receptor expression, a high response rate to chemotherapy, and a tendency for early metastasis, leading to a generally poor prognosis. This study aims to evaluate the sociodemographic characteristics and clinical, pathological, and radiological features of patients diagnosed with TNBC; to assess their response to neoadjuvant chemotherapy (NACT), identify predictive factors associated with treatment outcomes, and evaluate their effect on disease-free survival (DFS) and overall survival (OS). Between December 2012 and September 2017, 90 female patients diagnosed with stage IIA-IIIB TNBC were retrospectively enrolled in the study from the Breast Surgery Clinic, Department of General Surgery, at İstanbul Medipol University.All patients received standardized treatment protocol beginning with NACT, followed by surgery. Inclusion criteria were confirmed TNBC diagnosis, female sex, age between 30-65 years, no history of prior malignancy, and full adherence to treatment and follow-up protocols. Exclusion criteria included: age outside the specified range, presence of distant metastasis at diagnosis, deviation from treatment or follow-up protocols, and non-cancer-related death during the study period. The data obtained during the study were examined in two separate sections. In the first section, patients were categorized into two subgroups based on whether they achieved a pCR following NACT, to assess the predictability of tumor response to treatment. This section focused on identifying factors associated with achieving pCR. In the second section, the impact of pCR on DFS and OS was examined in all patient- and disease-related variables.The continuous variables assessed using the Shapiro-Wilk test. Variables with normal distribution analyzed using the Student’s t-test, while non-normally distributed variables were analyzed with the Mann-Whitney U test. Categorical variables were evaluated using the Chi-square test, Fisher’s Exact test, and the Fisher-Freeman-Halton test. A total of 84 women with stage IIA-IIIB TNBC were included. The mean age was 49.1±11.5 years. pCR was achieved in 24 patients (28.6%). pCR was significantly associated with postmenopausal status (p = 0.04), smaller tumor size (p = 0.04), higher biopsy Ki-67 (p = 0.02), lower postoperative Ki-67 (p < 0.001), negative clinical and pathological nodal stage, low tumor grade, absence of lymphovascular invasion (LVI) and necrosis, and no axillary involvement at surgery (p < 0.05). MRI and PET-CT responses were strong predictors of pCR (p < 0.001)BRCA1/2 mutation status, tumor subtype, clinical T and N stage, pre-treatment tumor size, MRI and PET-CT response, residual tumor size, presence of LVI and necrosis, pCR status, and postoperative ki-67 level all associated with both DFS and OS. Biopsy ki-67 associated only with OS (p = 0.006). Notably, a postoperative ki-67 value of <10% was associated with significantly better survival outcomes.pCR and low postoperative Ki-67 levels were the strongest predictors of improved DFS and OS. Patients who were postmenopausal and had high biopsy Ki-67 values were more likely to achieve pCR. Although menopausal status and initial Ki-67 were not directly prognostic, their strong association with pCR indirectly linked them to better outcomes. These findings highlight the importance of treatment response in TNBC prognosis and support further multicenter studies to validate these markers in broader populations. Citation Format: M. Zencıroglu, P. Abbasoglu, O. H. Topgul, P. Basım. The Impact of Pre-Treatment Clinical, Pathological, and Radiological Parameters on Pathological Complete Response and Prognosis Following Neoadjuvant Therapy in Patients with Triple-Negative Breast Cancer [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 PS4-10-17.