Refining the indications for neoadjuvant chemotherapy for patients with HER2+ breast cancer: A single institution experience.

Background: We aim to compare the clinical outcomes of patients with early-stage HER2+ breast cancer treated with adjuvant chemotherapy (AC) and neoadjuvant chemotherapy (NAC).

Methods: Patients with non-metastatic HER2+ breast cancer treated from 2009 to 2018 at our institution comprised our study cohort (n = 1254). Pathologic complete response (pCR) was defined as the absence of invasive disease in the breast and axilla after NAC. Log-rank, Kaplan-Meier, and inverse probability of treatment weighting were used to assess differences in disease-free and overall survival between groups stratified by AC vs. NAC and pCR vs. non-pCR.

Results: The majority received AC (n = 787 or 62.8%) while 467 (37.2%) patients received NAC. Median follow up for AC and NAC groups was 46 and 28 months, respectively. The crude disease-free survival and overall survival of our study cohort were 92.2% and 89.1% for AC, 89.1% and 82.2% for NAC pCR, and 68.1% and 60.0% for NAC non-pCR, respectively. For clinical stage ≥IIB patients, NAC conferred a positive but statistically nonsignificant treatment effect over AC in multivariate analysis.

Conclusions: After adjusting for imbalances in our subgroups, we found that, regardless of the sequence of chemotherapy (AC vs. NAC), patients with early-stage HER2+ breast cancer had excellent outcomes.