A PROSPECTIVE OBSERVATIONAL STUDY ON PATHOLOGICAL COMPLETE RESPONSE IN HER2-POSITIVE BREAST CANCER

Background: Pathological complete response (pCR) is recognized as a key prognostic factor in breast cancer, particularly in HER2-positive subtypes. Achieving pCR following neoadjuvant chemotherapy (NACT) correlates with improved long-term outcomes, including overall survival (OS) and disease-free survival (DFS). Objectives: This study aims to assess the prognostic significance of pCR in HER2-positive breast cancer and to evaluate the rates of pCR, defined as the absence of invasive cancer in the breast and axillary lymph nodes after completion of NACT and surgical intervention. Methods: A prospective observational study was conducted at the Department of Medical Oncology, Bharath Hospitals and Institute of Oncology, Mysuru, spanning a duration of six months. After obtaining informed consent, data from 70 HER2-positive breast cancer patients were collected and analyzed using immunohistochemistry (IHC) reports, pathological grading, breast cancer staging systems, BI-RADS categories, and histopathology findings. Results: Among the 70 patients diagnosed with HER2-positive breast cancer, targeted therapy regimens were administered as follows: 38.57% received the TCH protocol (docetaxel, carboplatin, trastuzumab), while 25.71% were treated with TCHP (TCH combined with Pertuzumab). Neoadjuvant chemotherapy regimens included AC + Paclitaxel in 15.71% of patients, Paclitaxel monotherapy in 12.85%, and the AC regimen alone in 7.14%. The overall pathological complete response (pCR) rate observed was 37.14%. Conclusion: Achieving pCR is strongly associated with improved long-term outcomes, notably enhanced OS and event-free survival (EFS) in HER2-positive breast cancer. The integration of advanced targeted therapies has significantly improved treatment efficacy and prognosis in this aggressive breast cancer subtype.