Background:Trastuzumab was introduced a decade ago and has improved outcomes for HER2-positive breast cancer. We investigated the factors predictive of pathological complete response (pCR), prognostic factors for disease-free survival (DFS), and interactions between pCR and DFS after neoadjuvant treatment.Methods:We identified 287 patients with primary HER2-positive breast cancers given neoadjuvant chemotherapy (NAC) between 2002 and 2011. Univariate and multivariate analyses of clinical and pathological factors associated with pCR and DFS were performed.Results:pCR rates differed between patients receiving neoadjuvant trastuzumab treatment or not (47.7% versus 19.3%, P<0.0001). DFS also differed significantly between patients receiving adjuvant trastuzumab or not (hazard ratio=4.84, 95% CI (2.52; 9.31), P<0.001). We analysed 199 patients given neoadjuvant and adjuvant trastuzumab. Multivariate analysis identified older age and hormone receptor-negative tumours as independent predictors of pCR. T stage (hazard ratio=2.55, 95% CI (1.01; 6.48), P=0.05) and strict pCR (hazard ratio=9.15, 95% CI (1.22; 68.83), P=0.03) were independent predictors of DFS. The latter association was significant in the HR-negative subgroup (P=0.02) but not in the HR-positive subgroup (P=0.12).Conclusions:Major pCR and DFS gains in HER2-positive BC were observed since ‘trastuzumab' era. Further improvements rely on the enrollment of accurately selected patients into clinical trials.

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