Author: By Lynda Williams, Senior medwireNews Reporter
medwireNews: The second interim analysis of the MONALEESA-3 trial has demonstrated a significant overall survival (OS) improvement for women with hormone receptor (HR)-positive, HER2-negative advanced breast cancer with the use of ribociclib and fulvestrant versus fulvestrant alone.
At 42 months, 57.8% of the 484 patients randomly assigned to receive ribociclib plus fulvestrant were alive versus 45.9% of the 242 patients who instead received placebo plus fulvestrant, giving a significant hazard ratio (HR) for death of 0.72 in favour of the CDK4/6 inhibitor.
Median OS in the phase III trial was not reached with ribociclib plus fulvestrant versus 40.0 months with placebo plus fulvestrant.
As the OS results crossed the prespecified efficacy criteria for stopping, this will be the final analysis of the trial protocol, reported Dennis Slamon, from the UCLA Translational Oncology Research Lab in Santa Monica, California, USA, at the San Antonio Breast Cancer Symposium in Texas, USA.
The study findings – also reported in The New England Journal of Medicine – demonstrated that the OS “benefit was consistent across most subgroups” although the confidence intervals were wide for some subgroups with small patient numbers. This included a significant benefit with ribociclib use regardless of whether patients received the trial regimen first-line (HR=0.70) or had an early relapse or received the regimen as a second-line (HR=0.73) therapy.
The investigators also reported a descriptive update for progression-free survival for the first-line therapy subgroup, with a median duration of 33.6 months with ribociclib plus fulvestrant versus 19.2 months for placebo and fulvestrant.
“This finding, together with data on overall survival, may support consideration of ribociclib plus fulvestrant as initial therapy in patients with advanced disease”, they write, noting that the results also support its use among patients with early relapse and as a second-line therapy.
The team concludes: “The combinations of ribociclib with fulvestrant in the MONALEESA-3 trial and with endocrine therapy, particularly nonsteroidal aromatase inhibitors, in the MONALEESA-7 trial have shown a consistent and meaningful prolongation of survival over placebo.
“Indeed, both trials showed an approximate 30% difference in the relative risk of death with ribociclib as compared with placebo in combination with different endocrine-therapy partners, regardless of menopausal status in patients with hormone receptor–positive, HER2-negative advanced breast cancer.”
Slamon DJ, Neven P, Chia S, et al. Overall survival with ribociclib plus fulvestrant in advanced breast cancer. N Engl J Med; Advance online publication 11 December 2019. DOI: 10.1056/NEJMoa1911149
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