Analysis of associations between molecular subtypes and responses to neoadjuvant chemotherapy in primary breast cancer patients

Abstract

To explore the correlations between molecular subtypes and responses to neoadjuvant chemotherapy in primary breast cancer patients. The core-needle biopsy specimens were collected from 563 patients undergoing 4-8 cycles of neoadjuvant chemotherapy between January 2001 to January 2009. And immunohistochemical assays were employed to detect the levels of estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2) and Ki-67 proliferation index simultaneously. Molecular subtypes were divided on the basis of immunohistochemical results. And the associations between molecular subtypes and responses to neoadjuvant chemotherapy were analyzed in 563 patients. The pathological complete response (pCR) rates of patients with hormone receptor-negative/HER2-negative subtype (HR-/HER2-) , HER2-positive subtype (HER2+) and hormone receptor-positive/HER2-negative subtype (HR+/HER2-) were 38.9%, 17.9% and 8.3% respectively. In univariate analysis, there were significant differences in pCR rates among the groups (P < 0.001) . In multivariate analysis, the patients with HER2+ subtype had a significantly higher pCR rate than those with HR+/HER2- subtype (OR = 0.344, P = 0.002) . Whereas the patients with HER2+ subtype had a significantly lower pCR rate than those with HR-/HER2- subtype (OR = 2.453, P = 0.007) . Among HR+/HER2-subtypes, a higher pCR rate was observed in the group of high expression level of Ki-67 proliferation index (Ki-67 ≥ 20%) (P = 0.004) . But no significant differences existed in pCR rates between the group of high expression level of hormone receptor and the group of non-high expression level (P = 0.256) . There were correlations between molecular subtypes and responses to neoadjuvant chemotherapy in primary breast cancer patients. Patients of HER2+and HR-/HER2- subtype are more likely to respond to neoadjuvant chemotherapy. Among HR+/HER2-subtypes, those with a high level of Ki-67 proliferation index tend to benefit from neoadjuvant chemotherapy.