OBJECTIVETo investigate the predictive factors of pathological complete response (pCR) in primary human epidermal growth factor receptor 2 (HER2)-positive breast cancer treated with trastuzumab-based neoadjuvant chemotherapy (NAC).

METHODSTotally 101 patients of primary HER2-positive breast cancer treated with trastuzumab-based NAC and subsequent curative surgical therapy in the Breast Disease Center of Peking University First Hospital from September 2007 to December 2014 were retrospectively reviewed. All patients were female with a median age of 53 (range 23 to 70) years.All patients received a taxanes- and carboplatin-containing chemotherapy, and trastuzumab was administered concurrently.A pCR, defined as the absence of invasive tumor cells in the breast and axillary lymph nodes, was achieved in 37.6% of patients (38/101). For analysis of the associations between clinicopathological factors and pCR, the χ(2) test or Fisher's exact test was used for univariate analysis, and multivariate Logistic regression analysis was performed to estimate OR and 95% CI.

RESULTSTumor-infiltrating lymphocytes (χ(2)=14.981, P=0.000), hormone receptor (HR) status (χ(2)=9.513, P=0.002), and tumor grade (χ(2)=4.005, P=0.045) were significantly associated with pCR in univariate analysis. Tumor-infiltrating lymphocytes positive (OR=4.74, 95% CI: 1.87 to 12.01, P=0.001) and HR-negative (OR=3.28, 95% CI: 1.31 to 8.20, P=0.011) were independent predictive factors of pCR in multivariate analysis.

CONCLUSIONTumor-infiltrating lymphocytes-positive and HR-negative were independent predictive factors of pCR in primary HER2-positive breast cancer treated with trastuzumab-based NAC.