The subgroup of East Asian women with hormone receptor (HR)-positive, HER2-negative advanced breast cancer and disease progression on endocrine therapy participating in the phase III MONARCH 2 study continued to show improved survival outcomes compared to placebo plus fulvestrant at approximately 4-year follow-up, according to findings presented at the ESMO Asia Virtual Congress 2020, held from 20 to 22 November 2020.
According to Chiun-Sheng Huang of the National Taiwan University Hospital in Taipei, Taiwan the global, double-blind, randomised phase III MONARCH 2 (NCT02107703) study demonstrated that abemaciclib/fulvestrant had a manageble safety profile and the combination significantly improved median progression-free survival (PFS) to 16.4 months versus 9.3 months with placebo/fulvestrant (hazard ratio [HR] 0.553; p < 0.001) and prolonged median overall survival (OS) to 46.7 versus 37.3 months, respectively (HR 0.757; p = 0.01), providing an OS benefit of 9.4 months in patients with HR-positive, HER2-negative advanced breast cancer who progressed on endocrine therapy.
Furthermore, previously reported findings from the study showed that data from the subgroup of patients enrolled from Japan, Korea, Taiwan were consistent with the intent-to-treat (ITT) population and with patients from other regions; median PFS in this subgroup was 21.2 months with abemaciclib/fulvestrant compared to11.6 months with placebo/fulvestrant (HR 0.520; p < 0.001).
MONARCH 2 enrolled 669 patients with HR-positive, HER2-negative advanced breast cancer and progression on endocrine therapy. Eligible patients included pre- or perimenopausal on ovarian suppression and postmenopausal who were randomised 2:1 to receive continuous abemaciclib at 150 mg every 12 hours or placebo; both treatment arms also were treated with fulvestrant at 500 mg per label. Exploratory subgroup analyses were done on East Asian patients in the ITT population.
At ESMO Asia Virtual Congress 2020, Professor Huang presented OS and other updated efficacy findings at 4-year follow-up, as well as safety data for the East Asian subgroup in the MONARCH 2 study.
Updated findings all favoured abemaciclib plus fulvestrant over placebo plus fulvestrant
The ITT population contained 212 East Asian patients of whom 147 were treated with abemaciclib plus fulvestrant and 65 received placebo plus fulvestrant; at data cut-off on 20 June 2019, 89 OS events had occurred in these patients.
At this time, median OS was not reached (NR) for abemaciclib/fulvestrant compared to 48.9 months with placebo/fulvestrant (HR 0.798; 95% confidence interval [CI] 0.515-1.235; p = 0.38). The 42 month OS rates were 64% (95% CI 55.5-71.8) with abemaciclib/fulvestrant compared to 53% (95% CI 39.9-64.6) with placebo/fulvestrant.
In addition, significantly improved outcomes favouring abemaciclib/fulvestrant over placebo/fulvestrant were observed for time-to-second-objective-disease-progression (PFS2) (HR 0.588; 95% CI 0.420-0.823; p = 0.001), time to chemotherapy (HR 0.601; 95% CI 0.411-0.877; p = 0.008), and chemotherapy-free survival (HR 0.573; 95% CI; 0.402-0.815; p = 0.002).
The safety profile in the East Asian patients was consistent with previously reported safety data and no new safety signals were reported.
The authors noted that findings from this update were consistent with previous reports in the ITT and East Asian populations. In the long-term, abemaciclib plus fulvestrant was an effective and tolerable treatment for East Asian patients with HR-positive, HER2-negative advanced breast cancer who progressed on endocrine therapy.
Funding was reported from Eli Lilly and Company.
45O – Huang C-S, Toi M, Im Y-H, et al. Abemaciclib plus fulvestrant in East Asian women with HR+, HER2- advanced breast cancer: Overall Survival from MONARCH 2. ESMO Asia Virtual Congress 2020 (20 to 22 November).