Pathological and clinical outcomes following neoadjuvant dual HER2 therapy for early‐stage breast cancer: An Australian institutional real‐world experience

Abstract

Abstract Aim There has been significant progress made in developing novel targeted therapies in the neoadjuvant setting for non‐metastatic HER2‐positive breast cancer, which may be used in combination with conventional chemotherapy to optimise pathological responses at surgery. However, these therapies, particularly the chemotherapeutic components, may portend significant and long‐lasting toxicity. Hence, de‐escalation of treatment intensity has been an area of interest and was evaluated in the phase II NeoSphere study. Herein, we report the real‐world pathological and survival outcomes from neoadjuvant taxane and dual HER2 blockade recorded at our centre. Methods This was a retrospective cohort study of patients receiving neoadjuvant pertuzumab, trastuzumab and taxane chemotherapy for non‐metastatic HER2‐positive breast cancer at a single centre in Sydney, Australia. We collected data pertaining to baseline demographic characteristics, pathological response rates, post‐surgical prescribing patterns and also undertook survival analyses for invasive disease‐free survival (iDFS) as well as exploratory analyses for correlations between pre‐specified clinicopathologic factors and pathological response at surgery. Results Our population was largely similar at baseline to the NeoSphere study. 71 patients were included in the final analysis. 61% achieved a pathological complete response (pCR). Three patients received conventional chemotherapy in the adjuvant setting. 92% of included patients were alive and disease‐free at 3 years of follow‐up. Only 3 events of recurrence or death were recorded at a median follow‐up of 32 months. No significant difference in iDFS was noted between patients achieving pCR and those with residual disease at surgery. Conclusion This study demonstrates that de‐escalated adjuvant treatment for HER2‐positive early breast cancer achieved favourable pathological and long‐term outcomes comparable to large trials, some utilising more intensive chemotherapeutic components.