Impact of adjuvant chemotherapy with respect to level of hormone receptor expression in patients with hormone responsive breast cancer: Implications for endocrine resistance

Abstract

11563 Background: The efficacy of hormone therapy (HT) is controversial in patients with a lower level of estrogen receptor (ER) expression or absence of progesterone receptor (PR). The aim of this study is to compare the efficacy of adjuvant HT and chemotherapy (CT) +HT in patients with different levels of ER and PR expression. Methods: 190 patients with nonmetastatic hormone responsive breast cancer and a median follow-up period of 49 months were included in this study. Fifty percent of patients were premenopausal and 63% were node positive. Both HR were evaluated by immunohistochemistry. ER expression score, as assessed by the ratio or percentage of cells stained positive, was evaluated in 4 groups: negative (8%), <1/3 (29%), ≥1/3–2/3 (18%), >2/3 (45%); whereas, patients were classified as positive or negative (19%) with respect to PR expression. The number of patients who received CT/HT and HT in the high ER score group and ER+/PR- groups were 63 (77%)/19 (23%) and 27 (82%)/6 (18%), as compared to low ER 44 (83%)/9 (17) and ER+/PR+ groups 121 (81%)/7 (21%), respectively. The prognostic impact of these factors on overall (OS) and disease-free survival (DFS) were analyzed by the Kaplan-Meier method. Results: The use of adjuvant CT was significantly higher in patients with node positive disease regardless of ER score or PR expression. OS and DFS were significantly lower in patients with a negative ER (p=0.02). There was no difference in either endpoint with respect to expression score. There was a trend for poorer DFS and OS (p=0.08) in PR negative patients. There was no additional efficacy of CT with respect to ER score or PR expression. Conclusions: In this data set adjuvant CT seems to offer no additional benefit in ER positive patients regardless of ER score of PR expression. Other factors should be evaluated to predict endocrine resistance in patients with hormone responsive disease. Mature data with longer follow-up is pending. No significant financial relationships to disclose.