Relationship between survival and estrogen receptor (ER) status in pts with metastatic breast cancer (MBC) treated with capecitabine (C) and docetaxel (D): An exploratory data analysis

Abstract

1024 Background: Previous studies in pts with MBC have shown that women with ER+ tumors have a longer survival time compared to women with ER- tumors. An exploratory analysis was conducted to describe the relationship between survival and ER status among MBC pts treated with combination therapy consisting of C+D. Methods: This analysis used data from an open-label, randomized phase III trial of C+D vs D alone in pts with advanced and/or MBC. Survival analysis was used to investigate the effect of baseline ER status of the primary and metastatic tumors on overall survival (OS). ER status was defined as positive if positive for any tumor, negative if at least 1 negative test, otherwise unknown. Results: Among 506 intent-to-treat pts (randomized, received ≥1 dose), ER status was identified in 356. C+D: 90 ER+, 88 ER-; D alone: 95 ER+, 83 ER-. The unadjusted log-rank test showed a significant difference in OS between the C+D and D groups for ER+ but not ER- pts. In the ER+ group, median OS was longer in C+D vs D pts (538.5 vs 379.0 d) (hazard ratio [HR] 0.65; P=0.007). OS was significantly longer in ER+ vs ER- pts in the C+D group (538.5 vs 329.0 d) (HR 0.68; P=0.019) but not in the D group (379.0 vs 301.0 d) (HR 0.90; P=0.514). OS by time from diagnosis to recurrence and baseline tumor size showed no significant differences between ER+ and ER- pts. Conclusions: This exploratory analysis suggested a significant difference in OS between the C + D and D groups in ER+ (HR 0.65) but not ER- (HR 0.90) pts. Also, within the C+D group, the median OS was significantly longer in ER+ than ER- pts (HR 0.68). [Table: see text] [Table: see text]