Abstract P2-09-22: Predictive Significance of the Proportion of ER-or PgR-Positive Tumor Cells in Neoadjuvant Chemotherapy for Operable HER2-Negative Breast Cancer

Abstract

Abstract Background Estrogen receptor (ER) and progesterone receptor (PgR) status are predictive for clinical and pathological response in neoadjuvant chemotherapy for operable breast cancer. However, it remains unclear how the proportion of ER-or PgR-positive staining tumor cells affect responses to neoadjuvant chemotherapy. The purpose of this study was to examine the correlation of the proportion of ER-or PgR-positive staining tumor cells with the clinical and pathological responses to neoadjuvant chemotherapy for operable HER2-negative breast cancer. Patients and Methods From April 2002 to May 2010, 101 patients received neoadjuvant chemotherapy containing epirubicin and taxane in our clinic. We assessed menopausal status, tumor size, lymph node status, histological grade, ER, PgR, p53 and Ki-67. In this study, we defined the positivity of ER and PgR as more than or equal to 1% of the positive staining tumor cells according to ASCO/CAP announcement in April 2010. Furthermore, patients with ER-positive tumor were divided into two groups at 30% of ER positive staining tumor cells. Results A clinical response was seen in 82% of all patients and a pathological complete response (pCR) was seen in 17%. Of the 101 patients, 60 (59%) had ER-positive tumors and 38 (63%) of the patients had tumors with more than 90% of ER-positive staining cells. Also, 52 (51%) had PgR-positive tumors. Fourteen (34%) of the 41 patients with ER-negative tumors achieved a pCR and 15 (31%) of the 49 patients with PgR-negative tumors achieved a pCR. Patients with more than 30% of ER-or more than 1% of PgR-positive staining tumor cells did not achieve a pCR. There was no significant correlation of pCR with menopausal status, tumor size, grade and Ki-67. In univariate analysis, a pCR was associated with ER status (p=0.0001), PgR status (p=0.0001), and chemotherapy regimens (p=0.014). Multivariate analysis revealed that ER status was a significant factor for pCR, and patients with ER-negative tumors were 20.1 times more likely to achieve a pCR than those with more than or equal to 30% tumors staining tumor cells (p=0.005; 95% confidential interval, 2.5-16.5). Conclusion We demonstrated a predictive significance of the proportion of ER-or PgR-positive tumor cells in neoadjuvant chemotherapy for operable HER2- negative breast cancer. ER-negativity (<1%) is significantly predictive to achieve a pCR in multivariate analysis. Conversely, it seems very possible that patients with more than 30% ER-or more than 1% PgR-positive staining tumor cells do not achieve a pCR. It is important to take the proportion of ER-and PgR-positive staining tumor cells into consideration in the treatment of breast cancer. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P2-09-22.