Clinicopathological Factors Associated with Pathological Complete Response After Neoadjuvant Chemotherapy in Breast Cancer: A Single-Center Retrospective Study

Objective: This study aimed to determine the pathological complete response (pCR) rate and evaluate clinicopathological factors associated with pCR in patients with breast cancer who underwent surgery after neoadjuvant chemotherapy (NAC).Materials and Methods: We retrospectively reviewed 53 women who received NAC followed by surgery at a single center between January 2019 and August 2024. Demographic characteristics, clinical stage, histological grade, estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2) status, and Ki-67 proliferation index were evaluated. pCR was defined as the absence of residual invasive tumor in the breast and sampled axillary lymph nodes after neoadjuvant treatment. Factors associated with pCR were assessed using univariable and multivariable binary logistic regression analyses.Results: The mean age at diagnosis was 51.09 ± 10.07 years. pCR was achieved in 19 of 53 patients (35.8%). The pCR rates by molecular subgroup were 9.1% (2/22) in HR-positive/HER2-negative, 45.0% (9/20) in HR-positive/HER2-positive, 100% (3/3) in HR-negative/HER2-positive, and 62.5% (5/8) in triple-negative breast cancer. In multivariable analysis, grade III tumors were associated with higher odds of pCR than grade II tumors (OR 92.07; 95% CI 9.17–924.63; p<0.001). HER2 positivity was also independently associated with pCR compared with HER2 negativity (OR 9.71; 95% CI 1.04–90.48; p=0.046).Conclusion: In this single-center retrospective study, high histological grade and HER2 positivity were independently associated with pCR after NAC. These findings support the potential importance of histological and biological tumor characteristics in predicting pathological response to neoadjuvant treatment. Validation in larger prospective cohorts is warranted.