Clinical and Prognostic Significance of Pathological Complete Response Following Contemporary Neoadjuvant Therapy in Triple Negative Breast Cancer: A Prospective Observational Study

Background Information: Pathological complete response (pCR) serves as a key prognostic indicator in breast cancer, particularly in triple-negative breast cancer (TNBC). Achievement of pCR following neoadjuvant chemotherapy (NACT) correlates with improved long-term outcomes, including enhanced overall survival (OS) and disease-free survival (DFS). Objectives: To evaluate the prognostic significance of pathological complete response (pCR) defined as the absence of residual invasive breast cancer in the breast and axilla following neoadjuvant chemotherapy (NACT) and surgical resection in triple-negative breast cancer (TNBC) patients. Methods: This prospective observational study, titled "Clinical and Prognostic Significance of Pathological Complete Response Following Contemporary Neoadjuvant Therapy in Triple- Negative Breast Cancer" was conducted over 6 months in the Medical Oncology Department at Bharath Hospitals and Institute of Oncology, Mysuru. Following written informed consent, eligible TNBC patients undergoing neoadjuvant chemotherapy (NACT) were interviewed to collect clinical and pathological data, including immunohistochemistry reports, tumor grading, AJCC/TNM staging, BI-RADS category, and histopathology, for assessing pathological complete response (pCR); all data were systematically recorded and analyzed descriptively. Results: This study enrolled 61 patients diagnosed with triple-negative breast cancer (TNBC). Neoadjuvant chemotherapy regimens included AC + paclitaxel (60.65%), paclitaxel alone (8.19%), and AC alone (31.14%). Pathological complete response (pCR) was achieved in 34.42% of TNBC patients. Conclusion: Achieving pathological complete response (pCR) following contemporary neoadjuvant therapy was observed in 34.42% of triple-negative breast cancer (TNBC) patients and correlates with improved long-term outcomes, including enhanced overall survival (OS) and event-free survival (EFS). These findings affirm pCR as a valuable early surrogate endpoint for treatment efficacy and a robust prognostic marker in TNBC.