Gene-Based Biomarker Identifies Patients With Breast Cancer More Likely to Respond to Enzalutamide

Wayne Kuznar
Published: Friday, Dec 08, 2017

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 = .0082).

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.


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