medwireNews: The final overall survival (OS) findings from the MONALEESA-2 trial confirm the long-term benefits of combining ribociclib with first-line letrozole for postmenopausal women with advanced hormone receptor (HR)-positive, HER2-negative breast cancer.
ESMO Congress 2021 session discussant Gonzalo Gomez-Abuin (Hospital Alemán, Buenos Aires, Argentina) praised the study findings, saying that “MONALEESA-2 is the first study to break the 5-year overall survival barrier in hormone receptor-positive, HER2-negative postmenopausal patients with metastatic breast cancer.”
Gabriel Hortobagyi (University of Texas MD Anderson Cancer Center, Houston, USA) presented the OS findings, following on from the previously reported positive progression-free survival results for the phase 3 trial.
The 334 patients randomly assigned to receive ribociclib 600 mg/day on a 3-weeks on, 1-week off schedule plus letrozole 2.5 mg/day had a median OS of 63.9 months versus 51.4 months for the 334 patients given placebo plus letrozole, giving a significant hazard ratio of 0.76.
Hortobagyi emphasized that the difference in the estimated OS rate between the study arms increased over follow-up, from a 5.7 percentage point difference between the two groups at 4 years, rising to a 12.2 percentage point difference after 6 years, when patients given the combination arm had an OS rate of 44.2% versus 32.0% for controls.
He noted that the OS benefit occurred despite patients given ribociclib plus letrozole being less likely to subsequently receive a CDK4/6 inhibitor after discontinuing their trial protocol than those given letrozole only (21.7 vs 34.4%). The combination arm also took significantly longer to require chemotherapy (median 50.6 vs 38.9 months, hazard ratio=0.74).
While there were no new safety signals in the study, Hortobagyi reported the grade 3–4 adverse events (AEs) of special interest for ribociclib plus letrozole compared with letrozole alone, namely neutropenia (63.8 vs 1.2%), hepatobiliary AEs (14.4 vs 4.8%), prolonged QT interval (4.5 vs 2.1%), and interstitial lung disease or pneumonitis (0.6 vs 0.0%).
“Ribociclib combined with endocrine therapy is the only first-line treatment with OS benefit and should therefore be considered as the preferred treatment option for HR+/HER2- advanced breast cancer,” the lead investigator concluded.
Hortobagyi added: “The MONALEESA trials with ribociclib demonstrate a consistent overall survival benefit regardless of endocrine therapy partner, line of therapy, or menopausal status.”
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