Survival outcomes of Zo-NAnTAx: a five-year analysis of zoledronic acid added to a neoadjuvant regimen for HER2-positive breast cancer.

Abstract

Zoledronic acid (ZA) improved outcomes in breast cancer. In pre-clinical studies, ZA increased tumour regression in combination chemotherapy and anti-human epidermal growth factor receptor 2 (HER2) target therapy. The Zo-NAnTax study, a clinical trial combining ZA with neoadjuvant therapy for HER2-positive tumours met the primary endpoint, showing a higher pathological complete response (pCR) rate than predicted in patients receiving surgery. Here, we report the exploratory relapse-free survival (RFS) and overall survival (OS) analysis after five years of follow-up. Adult women with HER2-positive breast cancer amendable to curative surgery who consented to the study received four cycles of ZA at 4 mg + doxorubicin 60 mg/m2 + cyclophosphamide 600 mg/m2 followed by four cycles of ZA at 4 mg + docetaxel 100 mg/m2 + trastuzumab 6 mg/kg (8 mg/kg as a loading dose), all in a 21 days-cycle, totalizing 8 cycles before surgery. To achieve the primary endpoint of pCR rate between 22% and 35%, 56 patients were needed. The secondary endpoints included safety, gene expression according to treatment response, prediction of pCR rate by an interim breast magnetic resonance imaging (bMRI). Beyond the overall pCR rate of 42%, alongside a good safety profile, we showed similar pCR rates in both hormonal receptor (HR) positive (40%) and HR-negative (44%). RFS and OS at five years were evaluated in 58 subjects, and the overall rate was 79.3% and 86.2%, respectively. Numerically higher values of both RFS and OS were observed in patients achieving pCR vs. non-achieving, respectively 83.3% vs. non-pCR 76.5% (P=0.57) and 95.8% vs. non-pCR 79.4% (P=0.08). Although not statistically significant, OS was numerically equivalent according to HR status, respectively 85.7% vs. 87.5% for HR-positive and HR-negative (P=0.91), which contrasted with RFS, HR-positive 81% vs. HR-negative 75% (P=0.58). None of the assessed clinicopathological biomarkers significantly correlated with survival. ZA plus neoadjuvant therapy in HER2-positive breast cancer shows provoking survival outcomes. Clinical and pre-clinical investigation with dual anti-HER2 blockage is warranted.