88 breast cancer patients who received NAC and surgery at our institute between January 2008 and March 2013 were enrolled. Staining results of ER, HER2, CK5/6, EGFR and Ki-67 were quantitated by automated immunostaining analysis. Patients were stratified into four grades (0, 1+, 2+, 3+) by ER status. Ki-67 index and nuclear grade were compared between a CK5/6- and/or EGFR-positive cohort and a CK5/6- and EGFR-negative cohort for each ER status grade. We also assessed response to chemotherapy according to ER, CK5/6 and EGFR status in a HER2 negative cohort.
The percentage of CK5/6- and/or EGFR-positive tumors decreased inversely with increasing degree of ER expression. In the ER0 cohort, the CK5/6- and/or EGFRpositive cohort had a higher Ki-67 index (p=.0875) and nuclear Grade 3 (p=.0036) than a CK5/6- and EGFR-negative cohort. A CK5/6- and/or EGFR-positive cohort showed a higher tumor reduction rate of clinical effect than a CK5/6- and EGFR-negative cohort (mean=57.3% and 24.6%, respectively, p=.2053) in an ER0 cohort. In the CK5/6- and/or EGFR-positive cohort, two of nine showed Grade 3 and seven showed Grade 2a or more of pathological effect. In cohorts of ER2+ or ER3+, there was no correlation between CK5/6 and EGFR status and response to chemotherapy.