Neoadjuvant chemotherapy-induced changes in immunohistochemical expression of estrogen receptor, progesterone receptor, HER2, and Ki-67 in patients with breast cancer.

PURPOSE: The impact of neoadjuvant chemotherapy (NACT) on immunohistochemical markers in breast cancer specimens remains controversial. We designed the current study to investigate the potential changes in estrogen receptor (ER), progesterone receptor (PR), HER2, and Ki-67 expression before and after NACT in a cohort of Turkish patients with breast cancer.

METHODS: This research was designed as a prospective, observational study of 100 consecutive patients with breast cancer (mean age 47.8±11.4 years) who were scheduled to undergo anthracycline- and/or taxane-containing NACT before attempting cytoreductive surgery at the Department of Oncology of the Uludag University Medical Center, Bursa, Turkey. Immunohistochemistry was performed on formalin-fixed, paraffin-embedded specimens.

RESULTS: Changes in immunohistochemical markers before and after NACT were only significant for HER-2 and Ki- 67. More specifically, the number of HER-2-positive specimens decreased from 21 before NACT to 8 after NACT (p<0.001). Similarly, the number of tumor samples positive for Ki-67 decreased significantly from 65 to 24 after NACT (p<0.001). Mean pre- and post-treatment tumor grades of differentiation before and after NACT were 2.56 ± 0.67 and 2.37±1.07, respectively (p<0.05). We did not find any significant associations between baseline ER, PR, HER2, and Ki-67 expression with both overall survival (OS) and disease- free survival (DFS).

CONCLUSION: Our study suggests that NACT reduces the expression of HER2 and Ki-67 in breast cancer specimens. The significance of NACT-induced changes in the immunohistochemical expression of HER2 and Ki-67 in patients with breast cancer should be further studied in future translational and clinical research.