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

Viola Vinita Dsa*, Amith M. N., Abhilash G. H., Charan C. S., Umesh M., Hanumanthachar Joshi

ABSTRACT

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.

Keywords: Breast Cancer, HER2-positive, Post NACT, pCR, Targeted Therapy.