Eribulin versus S-1 as first or second-line chemotherapy to assess health-related quality of life and overall survival in HER2-negative metastatic breast cancer (RESQ study): a non-inferiority, randomised, controlled, open-label, phase 3 trial.

Background: Eribulin prolongs overall survival (OS) of patients with human epidermal growth factor receptor 2 (HER2)-negative metastatic breast cancer (MBC), particularly in later chemotherapy (ChT) treatment. However, the health-related quality of life (HRQoL) and efficacy of first or second-line therapy in eribulin-treated patients remain unknown. Using eribulin in the first- or second-line may demonstrate the non-inferiority of HRQoL compared to S-1, an oral 5-fluorouracil derivative, while maintaining OS.

Methods: This randomised, controlled, open-label, phase III trial was conducted at 50 hospitals in Japan. Patients were enrolled from June 2016 and October 2019. Patients with HER2-negative MBC once under or no previous ChT were randomly assigned (1:1) to receive eribulin or S-1. HRQoL was assessed using the European Organization for Research and Treatment of Cancer (EORTC) Quality of Life Questionnaire-Core 30 (QLQ-C30) every six weeks until week 24 and every nine weeks until week 42. The primary endpoint was the deterioration defined as more than 10 points worsening of the general health score of QLQ-C30 or death within one year after randomisation. The secondary endpoints included OS. (Trial ID: UMIN000021398).

Findings: Three hundred and two patients were enrolled, with 152 and 148 assigned to the eribulin and S-1 groups, respectively. The questionnaire compliance rate was 85.6%. Risk difference of global health status deterioration through one year was -0.66% (95% CI: -12.47-11.16; non-inferiority P = 0.077) for eribulin compared to S-1 groups. Median time to first deterioration for global health status score was 5.64 (95% CI: 3.51-8.00) and 5.28 months (95% CI: 3.28-7.80) in the eribulin and S-1 groups, respectively. The median OS was 34.7 and 27.8 months, (HR: 0.72, 95% CI: 0.54-0.96; P = 0.026); the median progression-free survival was 7.57 and 6.75 months in the eribulin and S-1 groups, (HR: 0.88, 95% CI: 0.67-1.16; P = 0.35), respectively. No new adverse events occurred.

Interpretation: The time of the first clinical deterioration was similar between the two groups and OS significantly increased in eribulin-treated patients.

Funding: This study was funded by CSPOR-BC and Eisai CO., Ltd.