Locoregional Control According to Breast Cancer Subtype and Response to Neoadjuvant Chemotherapy in Breast Cancer Patients Undergoing Breast-conserving Therapy

Background: Our group previously published data showing that patients could be stratified by constructed molecular subtype with respect to locoregional recurrence (LRR)-free survival after neoadjuvant chemotherapy and breast-conserving therapy (BCT). That study predated use of trastuzumab for human epidermal growth factor receptor 2 (HER2)-positive patients. The current study was undertaken to determine the impact of subtype and response to therapy in a contemporary cohort. Methods: Clinicopathologic data from 751 breast cancer patients who received neoadjuvant chemotherapy (with trastuzumab if HER2⁺) and BCT from 2005 to 2012 were identified. Hormone receptor (HR) and HER2 status were used to construct molecular subtypes: HR⁺/HER2⁻ (n = 369), HR⁺/HER2⁺ (n = 105), HR⁻/HER2⁺ (n = 58), and HR⁻/HER2⁻ (n = 219). Actuarial rates of LRR were determined by the Kaplan–Meier method and compared by the log-rank test. Multivariate analysis was performed to determine factors associated with LRR. Results: The pathologic complete response (pCR) rates by subtype were as follows: 16.5 % (HR⁺/HER2⁻), 45.7 % (HR⁺/HER2⁺), 72.4 % (HR⁻/HER2⁺), and 42.0 % (HR⁻/HER2⁻) (P < 0.001). Median follow-up was 4.6 years. The 5-year LRR-free survival rate for all patients was 95.4 %. Five-year LRR-free survival rates by subtype were 97.2 % (HR⁺/HER2⁻), 96.1 % (HR⁺/HER2⁺), 94.4 % (HR⁻/HER2⁺), and 93.4 % (HR⁻/HER2⁻) (P = 0.44). For patients with HR⁻/HER2⁺ disease, the LRR-free survival rates were 97.4 and 86.7 % for those who did and those who did not experience pCR, respectively. For patients with HR⁻/HER2⁻ disease, the LRR-free survival rates were 98.6 % (pCR) versus 89.9 % (no pCR). On multivariate analysis, the HR⁻/HER2⁻ subtype, clinical stage III disease, and failure to experience a pCR were associated with LRR. Conclusions: Patients undergoing BCT after neoadjuvant chemotherapy have excellent rates of 5-year LRR-free survival that are affected by molecular subtype and by response to neoadjuvant chemotherapy.