Abstract P3-10-28: Breast Cancer Patients with Neoadjuvant Chemotherapy Have a Different Clinical Significance of the Ki-67 Expression before and after the Treatment

Abstract

Abstract Background: Reliable predictive and prognostic markers for routine diagnostic purposes are needed for breast cancer patients treated with neoadjuvant chemotherapy (NAC). Ki-67 is a marker for proliferating cells and is overexpressed in many breast cancers. Aim of this analysis was to evaluate the potential role of Ki-67 as a biomarker for the breast cancer patients with NAC. Patients and Methods: A retrospective search of a prospectively maintained clinical breast cancer database was performed to identify patients treated with NAC at the National Cancer Center Hospital East. The expression of Ki-67 was assessed using immunohistochemistry (MIB-1) in pretherapy core-needle biopsy and post-therapy surgical excision specimens. Levels of Ki-67 index (percentage of Ki-67 positive cancer nuclei) were dichotomized as high (over 10%) and low (less or equal 10%). Survival curve was calculated using Kaplan-Meier method. Log-Rank test was used to detect differences. Results: Records were available for 296 patients who were received NAC (anthracycline and/or taxane based) between Nov 2001 and Nov 2009. High and low Ki-67 index in pre-therapy were 173 and 123 cases, respectively. 51 cases (17%) of all achieved a pathological complete response (pCR: no residual invasive disease in the breast). pCR rate (23%) in high Ki-67 was significantly different from that (9%) in low Ki-67. 5-year overall survival estimates were 69% and 75%, respectively. However, there was not difference between the groups in overall survival curve at a median follow-up time of 31 months. Of 245 cases with residual invasive, high and low Ki-67 index in post-therapy were 80 and 165 cases, respectively. 62 cases maintained high Ki-67 index before and after NAC, 94 cases maintained low Ki-67 index. There was significantly difference between high and low Ki-67 indexes of post-therapy in overall survival curve (P<0.01), 5-year overall survival estimates were 51% and 81%, respectively. Moreover, there was not significant different between 51 cases with pCR and low Ki-67 index in overall survival curve. Conclusions: Although Ki-67 index in pre-therapy is a useful predictor for the therapeutic response to NAC, high Ki-67 index in pre-therapy dose not imply that the patients have a worse prognosis. Ki-67 index in post-therapy is useful to predict outcomes for patients with residual invasive disease. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P3-10-28.