336PCLINICAL IMPORTANCE OF DISCORDANCE IN HORMONE RECEPTOR AND HER2/NEU STATUS AFTER NEOADJUVANT CHEMOTHERAPY IN BREAST CANCER

Summary Purpose: The aim of this study was to compare the hormone receptors’ (HR) and HER2/neu status between core needle biopsy (CNB) and residual tumor after surgery of breast cancer treated with neoadjuvant chemotherapy (NAC), and also to evaluate the impact of discordance and other clinicopathological factors on survival. Methods: Oestrogen receptor (ER), progesterone receptor (PR) and HER2/neu status were evaluated by immunohistochemistry (IHC) on 90 CNBs of primary tumors and surgical specimens after NAC (study group); 53 patients without NAC served as control group, and discordance was compared between the two groups. The association between discordance of HR status after NAC and various other clinicopathological factors was tested with Spearman’s test. Results: Pathological complete response (PCR) was achieved in 10 (11.1%) patients after NAC. ER and PR changed significantly more in the study than in the control group. ER and PR discordance was detected in 10 (12.5%) and 17 (21.2%) patients in the NAC group and in 1 (1.8%) and 2 (3.7%) patients in the control group (p=0.04 and p=0.005, respectively). ER discordance was related with HER2/neu change. Furthermore, PR discordance correlated with CNB, ER and treatment response, while HER2/ neu discordance was associated with treatment response (p=0.05). ER discordance was found to be an independent prognostic factor for progression-free survival (PFS) (p=0.02). Conclusion: NAC might cause alterations in ER, PR or HER2/neu status in breast cancer, and they should be re-tested in the residual tumor after NAC to optimize ad juvant therapy.