Pathological Complete Response to Neoadjuvant Systemic Therapy in 789 Early and Locally Advanced Breast Cancer Patients: The Royal Marsden Experience

Purpose: Pathological complete response (pCR) after neoadjuvant chemotherapy (NACT) for breast cancer predicts the risk of recurrence and increasingly may indicate the need for additional therapy postoperatively.

Methods: We identified non-metastatic breast cancer patients receiving NACT during 2013-2017. Patients' and disease characteristics, rates of pCR (ypT0-is ypN0), toxicities, dose delays and reductions, and survival outcomes were recorded.

Results: 789 patients had median age of 50 years. 67.8% had stage II disease, 71.1% had grade 3 , and 91.8% had ductal histopathology. 32.8% had estrogen receptor (ER)-positive/human epidermal growth factor receptor 2 (HER2)-negative, 25.5% had triple-negative (TN), and 38.0% HER2-positive disease. 6.8% received platinum. 48.2% of the HER2-positive patients received trastuzumab and pertuzumab and 51.8% received trastuzumab. Overall pCR rate was 33.5% and differed according to disease subtype, receptor status, grade, histology, and early discontinuation, but not according to age, dose reductions/delays, or year of treatment. The addition of pertuzumab to trastuzumab marginally improved the pCR rates. Survival outcomes were better following pCR.

Conclusions: In our analysis, pCR rates are consistent with the published data. Even with contemporary therapies, many patients have residual disease following NACT, suggesting a significant risk of recurrence, and may benefit from additional postoperative systemic therapy.