Assessment of Pathological Response in Locally Advanced Breast Cancer Following Neoadjuvant Chemotherapy: A Single-Institution Retrospective Study

Introduction: Breast cancer is the most prevalent cancer among women in India, with approximately 200,000 new cases each year. Locally advanced breast cancer, classified as AJCC stages IIB to IIIC, accounts for 30 to 70 percent of these cases. This situation arises from delays in diagnosis, socioeconomic challenges, and issues in rural areas, contrasting with Western countries where early-stage breast cancer is more prevalent. These tumors are typically larger than 5 centimeters and often involve lymph nodes. They generally require neoadjuvant chemotherapy, usually consisting of doxorubicin and cyclophosphamide followed by taxanes, administered over six to eight cycles to reduce tumor size and facilitate surgery. The success rate of this treatment is between 70 to 90 percent, as reported in the NSABP B-18 study, which also evaluates tumor response to chemotherapy. A pathological complete response, defined as no remaining tumor in the breast or lymph nodes, occurs in about 10 to 20 percent of patients, with higher rates seen in those with HER2-positive or triple-negative breast cancer. This response strongly correlates with improved disease-free survival and overall survival, with hazard ratios ranging from 0.4 to 0.5 according to the CTNeoBC meta-analysis.

Objective: To Assess the Pathological Response in Locally Advanced Breast Cancer Following Neoadjuvant Chemotherapy

Methodology: This retrospective study looked at 176 patients who had biopsy-proven locally advanced breast cancer from the years 2020 to 2025. These patients completed neoadjuvant chemotherapy that was based on anthracycline and taxane before undergoing surgery, and there was post-neoadjuvant chemotherapy pathology data available which was categorized according to ypTNM as per the AJCC guidelines. Information was gathered on various factors including age, tumor side, number of treatment cycles, type of surgical procedure, tumor grade, and pathologic complete response, defined as ypT0 or Tis ypN0 or absence of residual tumor. This data was compiled using Excel and analyzed with SPSS version 16, with continuous variables reported as mean plus or minus standard deviation and categorical variables expressed as percentages.

Results: The results of our study on 176 patients with LABC (mean age: 53.7 ± 10.3 years) revealed that the tumor was equally likely to occur on either side and that the patients showed high compliance with neoadjuvant chemotherapy, with 85.2% completing 8 cycles and achieving 100% operability. The pathological characteristics showed that the majority of the patients had intermediate disease with T2 (31.8%) predominating over T1 and T3. The majority of the patients were node-negative with N0 (27.3%) and N1 (31.25%), indicating that the disease was in an early stage with respect to lymph node involvement. The pathological complete response was seen in 17.1%, which was slightly low in comparison with studies done in India.

Discussion: In our study of 176 LABC patients (mean age 53.7±10.3 years), high NACT compliance (85.2% completed 8 cycles) yielded 100% operability, intermediate pathology (T2 31.8%, ypN0 27.3%, N1 31.25%), and 17.1% pCR—slightly above Raina V6 et al. (2011; 7.8% pCR, 84.4% ORR, 58%/41% 5-year OS/DFS in n=128 northern Indian cases) and NSABP B-18 (13% pCR), but below Balaji A7 et al. (21.4% cPR in n=56 with significant T/N downstaging, P=0.001) and below to Mallige S8 et al. (12.2% pCR in n=50, HER2+ enriched). This aligns with Indian meta-analyses (10-22% pCR, biology/delay-influenced) and underscores taxane-responsive grades (O+ 41%), though regimen optimization (e.g., Dhanushkodi's NACR +6% pCR edge) was needed pending survival data.

Conclusion: Despite a moderate 17.1% pCR rate, which is comparable to Indian norms (10–22%) in the face of intermediate pathology and resource limitations, neoadjuvant chemotherapy achieved considerable downstaging and 100% operability in 176 LABC patients. These results support the usefulness of NACT for surgical optimization and highlight the necessity of regular pathological auditing and regimen improvement in Indian settings.