Determinants of pathological complete response to neoadjuvant chemotherapy in breast cancer: A single-institution experience

Background: Neoadjuvant chemotherapy (NACT) is routinely used in all cases of locally advanced breast cancer and some cases of early breast cancer. We previously reported a pathological complete response (pCR) rate of 8.3%. With the increasing use of taxanes and human epidermal growth factor receptor 2 (HER2)-directed NACT, we conducted this study to understand the current pCR rate and its determinants. Methods: A prospective database of breast cancer patients who underwent NACT followed by surgery between January and December 2017 was evaluated. Results: Of the 664 patients, 87.7% were cT3/T4, 91.6% were grade III, and 89.8% were node-positive at presentation (54.4% cN1, 35.4% cN2). The median age was 47 years; median pre-NACT clinical tumor size was 5.5 cm. Molecular subclassification was 30.3% hormone receptor positive (HR+) HER2-, 18.4% HR+HER2+, 14.9% HR-HER2+, and 31.6% triple negative (TN). Both anthracyclines and taxanes were given preoperatively in 31.2% patients whereas 58.5% of HER2 positive patients received HER2-targeted NACT. The overall pCR rate was 22.4% (149/664), 9.3% in HR+HER2-, 15.6% in HR+HER2+, 35.4% in HR-HER2+, and 33.4% in TN. On univariate analysis, duration of NACT (P < 0.001), cN stage at presentation (P = 0.022), HR status (P < 0.001), and lymphovascular invasion (P < 0.001) were associated with pCR. On logistic regression, HR negative status (Odds ratio [OR] 3.314, P < 0.001), longer duration of NACT (OR 2.332, P < 0.001), cN2 stage (OR 0.57, P = 0.012), and HER2 negativity (OR 1.583, P = 0.034) were significantly associated with pCR. Conclusion: Response to chemotherapy depends on molecular subtype and duration of NACT. A low rate of pCR in the HR+ subgroup of patients warrants reconsideration of neoadjuvant strategies.