Overall survival from the phase III postMONARCH trial of abemaciclib plus fulvestrant versus placebo plus fulvestrant for HR-positive, HER2-negative advanced breast cancer following progression on a prior CDK4/6 inhibitor plus endocrine therapy.

Abemaciclib plus fulvestrant in HR-positive, HER2-negative advanced breast cancer after progression on prior CDK4/6 inhibitor plus endocrine therapy showed numerically longer overall survival (32.1 vs 24.6 months; HR 0.80).

• Why it matters: Progression-free survival gains in this setting leave uncertainty about whether overall survival improves, which is critical for treatment decisions after CDK4/6 inhibitor failure.
• What they did: In the phase III postMONARCH trial, 368 participants were randomized 1:1 to abemaciclib plus fulvestrant or placebo plus fulvestrant, with final OS analyzed at 200 events using Kaplan-Meier and stratified Cox models.
• The result: At the data cut-off (median follow-up ~37 months), 200 OS events occurred (90 vs 110), yielding HR 0.80 (95% CI 0.60–1.06; P=0.11), so significance was not reached, though results were consistent across subgroups.

AI summary of the abstract · may contain errors · not medical advice · read the paper.