Impact of Pathologic Complete Response on Local-Regional Recurrence and Survival in Patients Undergoing Neoadjuvant Systemic Therapy and Breast-Conserving Surgery.

Objective: We aimed to compare oncologic outcomes between patients achieving pathologic complete response (pCR) versus residual disease (RD) after receiving neoadjuvant systemic therapy (NST) and breast-conserving surgery (BCS).

Methods: Our institutional database was used to identify patients treated with NST and BCS for cT1-3N0 invasive breast cancer. Overall survival (OS), disease-specific survival (DSS), local-regional recurrence-free survival (LRRFS), and distant recurrence-free survival (DRFS) rates were compared between patients with pCR and RD. Multivariable analysis was used to identify factors associated with oncologic outcomes.

Results: Between 1999 and 2015, 732 patients received NST and BCS, with a median follow-up period of 7.1 years. Median age at diagnosis was 52 years. Most patients had clinical T2 (78.8%). pCR differed significantly by tumor subtype, with larger proportions of patients with human epidermal growth factor receptor 2-positive (HER2+; 42.9%) and triple-negative (46.2%) breast cancer (TNBC) achieving pCR compared with hormone receptor-positive (HR+)/HER2-negative (HER2-; 15%) disease (p < 0.0001). Patients achieving pCR had significantly improved 5-year OS (p = 0.002), DSS (p = 0.02), and DRFS (p = 0.01) compared with those with RD. There were no significant differences in LRRFS between patients with pCR and RD, and the 5-year LRR rates were low, except in patients with TNBC and RD. On multivariate analyses, oncologic outcomes differed significantly by tumor subtype, with TNBC subtype associated with worse OS, DSS, LRRFS, and DRFS.

Conclusions: pCR is associated with improved OS, DSS, and DFRS. LRR rates were low, regardless of pCR or RD, in all tumor subtypes except TNBC.