Comparison of Protein Expression and Molecular Subtype in Breast Cancer before and after Neoadjuvant Chemotherapy.
Ho-chang Lee, Hyesil Seol, Hyoungsuk Ko, In Ae Park. Seoul National University College of Medicine, Republic of Korea; Chungbuk National University College of Medicine, Cheongju, Republic of Korea
Background: Molecular expression as well as stage and grade are associated with the outcome of patients with breast cancer. The changes of certain molecules after chemotherapy (CT) will affect the response to CT and can determine the prognoses of the patients.
Design: Using immunohistochemistry, we evaluated the changes of expression of the estrogen receptor (ER), progesterone receptor (PR), c-erbB2, p53, bcl-2, and EGFR and Ki-67 proliferation index in the specimens obtained from 222 cases with breast cancer before and after neoadjuvant chemotherapy (NCT). Determination of HER2 status for molecular subtyping was done by fluorescence in situ hybridization (FISH) in equivocal cases.
Results: After NCT, 23 of 217 cases (10.1%) showed different ER expression. However, 54 of 217 (24.8%) revealed altered PR expression after NCT, 50 of which were decreased. The expression of HER2/neu changed from negative to positive in five cases(2.3%) and changed from positive to negative in 13 cases(6.0%) of 218 cases. The expression changes after NCT were shown in 18 of 170 (10.6%) for p53, 29 of 169 (17.2%) for bcl-2, 19 of 162 (11.7%) for EGFR. Using paired Student t-test, the Ki-67 proliferation index before and after NCT was significantly decreased (15.09% vs. 8.05%, p<0.001). The change of molecular subtype occurred in 29 cases(20.3%) of 143 cases. The change of molecular subtype was resulted from HER2 loss in 16 cases (11.2%), HER2 gain in three cases(2.1%), hormone receptor (HR) loss in nine cases(6.3%) and HR gain in two cases(1.4%).
Conclusions: PR expression and Ki-67 proliferation index were significantly decreased after NCT. The change of molecular subtype after NCT was resulted from chiefly HER2 loss and partly HR loss.
Wednesday, March 2, 2011 1:00 PM
Poster Session VI # 5, Wednesday Afternoon