Effects of core needle biopsy and subsequent neoadjuvant chemotherapy on molecular alterations and outcome in breast cancer

Objectives The aim of our study is to evaluate the effect of core needle biopsy (CNB) and subsequent neoadjuvant chemotherapy (NAC) on the expression of estrogen receptor (ER), progesterone receptor (PR), human epidermal growth hormone receptor 2 (HER2) and Ki67 in breast cancer, and the associated influencing factors. Materials and methods In this retrospective cohort study, 143 patients with primary operable breast cancer who received NAC were included. ER, PR, HER2 and Ki67 statuses were compared between pretreatment and posttreatment residual samples. A control group of paired core and excision tumors from 123 patients who did not receive NAC within the same study period was also assessed. Data on patients' clinicopathologic features were collected to identify associated influencing factors. Results Ki67 value significantly increased in excision tumors compared with paired core samples in controls without presurgery treatment (P<0.01), which was associated with the pathologic lymph node status and the interaction of PR and HER2 status (P=0.008 and 0.028, respectively). In 143 patients who underwent NAC, a significant decrease was observed in the expression of PR and Ki67 after NAC (P=0.003 and P<0.01, respectively). Further subgroup analysis showed that PR decrease was more obvious in premenopausal patients and Luminal A patients (P=0.006 and 0.002, respectively). Conclusion Core samples could provide more reliable information on determination of molecular subtype than surgical excisions. Decreases in PR and Ki67 expression following NAC could be used as positive prognostic factors. We recommend repeat testing of these biologic markers following NAC for the sake of better disease management. To the best of our knowledge, this is the most comprehensive study to analyze the effect of neoadjuvant chemotherapy on molecular alteration and its associated influencing factors after reporting a CNB-associated Ki67 increase in the same study.