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.