Abstract P6-13-01: Impact of the Number of Prior Chemotherapy Regimens on Overall Survival (OS) among Subjects with Locally Recurrent or Metastatic Breast Cancer Treated with Eribulin Mesylate: Results from the Phase III EMBRACE Study

Abstract

Abstract Background: The randomized, controlled, open-label, phase III EMBRACE study compared the efficacy and safety of eribulin mesylate (E7389) vs. treatment of the physician's choice (TPC) in heavily pretreated subjects with late-stage breast cancer. The study met its primary endpoint by showing that eribulin significantly prolonged OS vs. TPC (HR: 0.809; 95% CI: 0.660-0.991; p=0.041). This exploratory subgroup analysis aimed to determine the influence of the number of prior regimens on OS among eribulin-treated subjects. Methods: Eligible subjects had locally recurrent or metastatic breast cancer and had received 2-5 prior chemotherapy regimens, including an anthracycline and a taxane, with ≥2 of the regimens given for locally recurrent or metastatic disease. Subjects had to show progression on or within 6 months of the last chemotherapy regimen. Subjects were stratified by geographic region, HER2/neu status, and prior capecitabine treatment and then randomized 2:1 to receive eribulin 1.4 mg/m2 intravenously over 2-5 minutes on Days 1 and 8 every 21 days or an approved TPC. Results: A total of 762 subjects in 135 centers worldwide were randomized to receive either eribulin (n=508) or TPC (n=254). Subjects had a median age of 55 years, 92% were white, 76% were postmenopausal, and 81 % had taxane-refractory disease. Overall, 47% and 53% of subjects had received ≥3 and >3 prior chemotherapy regimens in total, respectively. Seventy-five percent and 25% of subjects received ≥3 and >3 prior chemotherapy regimens in total for locally recurrent or metastatic disease, respectively. Subgroup analysis identified consistently longer median OS with eribulin vs. TPC in subjects who received ≥3 prior chemotherapy regimens, both in total and specifically for locally recurrent or metastatic disease (Table). Lesser improvements in OS with eribulin vs. TPC were observed in subjects who received >3 prior chemotherapy regimens. The study was not powered to show statistical significance for this subgroup analysis. Conclusion: In this retrospective subgroup analysis, the OS benefit with eribulin appears greater for subjects with locally recurrent or metastatic breast cancer who received fewer previous therapies. Additional studies are underway to confirm these findings in less heavily pretreated patients. Table. Overall survival by treatment history vs. TPC Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P6-13-01.