In the biomarker-positive population, median PFS in cohort 1 was 16.5 months in the enzalutamide arm compared with 4.3 months in the placebo arm, corresponding to an HR of 0.44 (P
= .0335). In cohort 2, median PFS was not significantly different between the enzalutamide and placebo arms (6.0 vs 5.3 months; HR 0.55; P
= .1936). In the biomarker-negative population, there was no benefit to adding enzalutamide to exemestane in either cohort of patients. In the biomarker-positive population, the clinical benefit rate at 24 weeks was approximately 80% in the enzalutamide arm versus approximately 40% in the placebo arm (P
= .0012) while the overall response rate showed a trend in favor of enzalutamide that did not achieve significance (P
= .0877). There was no benefit to enzalutamide in cohort 2 of the biomarker-positive subset. There was no significant difference in achievement of these endpoints between treatment groups in the ITT population. In the biomarker-negative population, a significantly higher percentage of the placebo arm achieved complete benefit compared with the enzalutamide arm (P
The adverse event (AE) profile with enzalutamide was similar to those in previous clinical trials. AEs led to dose interruptions in 21.0% and 25.0% of patients randomized to enzalutamide in cohorts 1 and 2, respectively, compared with 20.6% and 15.0%, respectively, randomized to placebo. AEs leading to treatment discontinuation occurred at a rate of 14.5% and 18.3% in cohorts 1 and 2 of the enzalutamide arm, compared with 15.9% and 8.3%, respectively, in the placebo arm. The most common AEs reported in the enzalutamide arms were nausea (39%) in cohort 1 and fatigue (37%) in cohort 2.
- Krop I, Abramson V, Colleoni M, et al. Results from a randomized placebo-controlled phase 2 trial evaluating exemestane ± enzalutamide in patients with hormone receptor–positive breast cancer. In: Proceedings from the 2017 San Antonio Breast Cancer Symposium; December 5-9, 2017; San Antonio, Texas. Abstract GS4-07.
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- Campagnoli C, Pasanisi P, Castellano I, et al. Postmenopausal breast cancer, androgens, and aromatase inhibitors. Breast Cancer Res Treat. 2013;139:1-11.