Adding ribociclib to first-line letrozole significantly prolonged progression-free survival and was safe compared with letrozole alone among women aged 65 years or older with hormone receptor (HR)-positive, HER2-negative advanced breast cancer, according to a study presented at the European Cancer Congress (ECCO) 2017.1

The multicenter, double-blind, phase 3 MONALEESA-2 trial ( Identifier: NCT01958021) showed that frontline treatment with ribociclib plus letrozole significantly reduced the risk of progression or death by about 44% vs letrozole plus placebo among postmenopausal women with HR-positive, HER2-negative disease (hazard ratio [HR], 0.556; 95% CI, 0.429-0.720).

Because physiologic functioning, comorbidities, and concomitant medications may affect the risk-to-benefit ratio of combination regimens among older patients, researchers conducted a subgroup analysis of MONALEESA-2 to evaluate the efficacy and safety of adding ribociclib for women 65 years or older.

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Ribociclib significantly reduced the risk of progression or death by approximately 39% compared with placebo (HR, 0.608; 95% CI, 0.394-0.937). Median progression-free survival was not reached (95% CI, 19.3-not reached) in the ribociclib arm vs 18.4 months (95% CI, 15.0-not reached) in the placebo arm.

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At data cut-off, 60% of patients treated with ribociclib plus letrozole were still receiving treatment compared with 53% of those receiving letrozole alone. In the ribociclib arm, 22% discontinued therapy due to disease progression and 9% as a result of adverse events vs 35% and 3%, respectively, in the placebo arm.

The most common grade 3 to 4 adverse events occurring in significantly more patients treated with ribociclib were neutropenia and leukopenia.


  1. Sonke GS, Hart LL, Campone M, et al. Efficacy and safety of ribociclib (LEE011) + letrozole in elderly patients with hormone receptor-positive (HR+), HER2-negative (HER2˗) advanced breast cancer (ABC) in MONALEESA-2. Paper presented at: European Cancer Congress 2017; January 27-30, 2017; Amsterdam, Netherlands.