Comparative efficacy of neoadjuvant to adjuvant chemotherapy for the treatment of early-stage HER2 negative breast cancer: A population-based analysis.

Abstract

e12100 Background: The use of neoadjuvant treatment has increased over the past decade due to its ability to assess tumour sensitivity to systemic treatment in vivo, and to downstage women for increased breast conserving surgery. Recent studies have stratified patients with residual disease to receive additional treatment, which has resulted in meaningful improvements in survival. However, meta-analysis data suggest similar long-term outcomes for patients treated with neoadjuvant chemotherapy (NACT) compared to adjuvant chemotherapy (ACT) in historical randomized trials. The comparative efficacy in a real-world setting utilizing modern chemotherapy regimens is unknown. Methods: A retrospective review of the BC Cancer Breast Cancer Outcomes Unit (BCOU) was performed to identify patients with stage I-III HER-2 negative breast cancer treated with chemotherapy at the BC Cancer Agency from 2005-2010. Patients were then divided into 2 groups: those who received neoadjuvant chemotherapy (NACT) and those who received adjuvant chemotherapy (ACT). A matched analysis (age, stage, subtype) for patients treated with NACT vs ACT (matched 1:3) was then performed using a propensity scoring method to compare distant disease-free survival (DDFS), breast cancer specific survival (BCSS) and overall survival (OS). No patients received adjuvant chemotherapy for residual disease after NACT. Results: A total of 656 patients met the inclusion criteria, consisting of 164 NACT and 492 ACT cases. Median age was 49 years (37-68) in the NACT group vs 49 (37-65) in the ACT group (p = 0.71). The majority had stage 3 disease, 64% in both groups (p = 1.0). Most were hormone receptor positive (HR+), 67.1% vs 70.7% in the NACT vs ACT groups, respectively (p = 0.41). 5-year DDFS was 75% with NACT (95%CI 67, 82) and 77% with ACT (95%CI 72, 81), p = 0.87. 5-year OS for patients treated with NACT was 77% (95%CI 71, 84) and 80% (95%CI 75, 85) for patients treated with ACT, p = 0.33. 5-year BCSS was 80% with NACT (95% CI 70, 86) and 82% (95%CI 77, 86) with ACT, p = 0.75. Multivariate analysis for tumour size, nodal involvement and subtype are ongoing. Conclusions: The use of NACT compared to ACT in a population-based setting did not result in significant differences in DDFS, OS or BCSS. Acknowledging the comparative efficacy of these approaches will be informative to determine if the addition of subsequent adjuvant treatment for patients with residual disease after NACT will lead to differential benefits in a population-based setting.