Impact of the Histologic Pattern of Residual Tumor After Neoadjuvant Chemotherapy on Recurrence and Survival in Stage I–III Breast Cancer

Background Additional risk-stratification measures are needed in breast cancer patients with residual disease after neoadjuvant chemotherapy (NAC). We aimed to describe oncologic outcomes in a modern cohort treated with NAC, and evaluate the prognostic value of histologic pattern of residual tumor. Patients and Methods We included patients with stage I–III breast cancer treated with NAC and surgery from 2004 to 2014. Histologic pattern of residual tumor was evaluated by central pathology review when slides were available. Multivariable Cox regression was performed to evaluate factors associated with locoregional recurrence (LRR), recurrence-free survival (RFS), and overall survival (OS). Results Among 975 patients, median follow-up was 74.0 months and 10-year rates of LRR, RFS, and OS were 9.8%, 67.6% and 74.4%, respectively. Biologic subtype, pathologic node-positive disease, and pathologic complete response (pCR) were associated with outcomes. Among 666 (68.3%) patients with central pathology review, pattern of residual disease was not significantly associated with LRR. However, both scattered residual tumor and no/minimal response relative to a concentric pattern of response were significantly associated with inferior RFS (scattered: hazard ratio 2.0, p = 0.015; no/minimal response: hazard ratio 2.2, p = 0.021) and OS (scattered: hazard ratio 2.2, p = 0.026; no/minimal response: hazard ratio 2.5, p = 0.023). This finding was most prominent in patients with triple-negative breast cancer. Conclusions Patients with a scattered relative to concentric pattern of residual tumor after NAC had inferior RFS and OS, nearly as poor as those with no/minimal response. Histologic pattern of residual tumor may represent a novel prognostic measure, particularly in the triple-negative breast cancer population.