Effect of ER/PR Weak Expression on Neoadjuvant Chemotherapy.

Abstract Background: Neoadjuvant chemotherapy(NAC) is now a relatively standard treatment for advanced breast cancer. Many reporters suggest that the response rate of NAC on ER/PR positive breast cancer is lower than on ER/PR negative cancer. However, there are few reports regarding the effectiveness of NAC according to expression of ER/PR. The aim of this study is to assess the effect of NAC on ER/PR weak positive breast cancer compared with ER/PR negative and strong positive breast cancer.Patients and Methods: 495 patients who underwent NAC between 2001 and 2008 were included. The patients were treated with variable chemotherapy regimens. We analyzed the response rate to NAC by revewing the preoperative breast imaging study including breast US and postoperative pathologic report. ER/PR expression by IHC were scored as negative, weak positive, intermediate and strong positive. We compared weak positive group with negative and strong positive group. We assessed clinicopathologic characteristics, response rate, disease progression according to ER/PR expression and chemotherapy regimens.Results: There were 165(33.3%) of ER/PR negative, 47(9.5%) of weak positive and 207(41.8%) of strong positive, respectively. Most of preoperative clinical stage was stage IIIA, 166(39.6%). Mean age of patients was 46.7±10.1 year. The pathologic complete response(pCR) was 47(11.2%). In weak positive group, pCR, partial response, stable disease, progressive disease was 9(19.1%), 23(48.9%), 9(19.1%) and 6(12.8%), respectively. There was no significant difference between weak positive group and negative group. However, pCR was less(11(5.3%)) in strong positive group compared with weak positive group. (p=0.004). In patients treated with preoperative anthracycline-based NAC and taxen-based NAC weak positive group was similar to negative group. However, pCR rate of strong positive group was lower than other groups.Conclusion: The clinicopathologic behaviors and effect of NAC on weak positive breast cancer were similar to ER/PR negative breast cancer. Therefore, neoadjuvant chemotherapy might be more effective in ER/PR weak positive breast cancer rather than strong positive breast cancer. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 4157.