Real-World Outcomes of Ribociclib and Aromatase Inhibitor Use in First Line Hormone Receptor Positive, HER2-Negative Metastatic Breast Cancer.

Background: International guidelines recommend combining a CDK4/6 inhibitor and endocrine therapy (ET) as first line treatment for hormone receptor (HR) positive, HER2 negative metastatic breast cancer (MBC). Results from MONALEESA-2 demonstrate superior progression free survival (PFS) and overall survival (OS) with ribociclib (CDK4/6 inhibitor) and ET compared to ET alone. Real world outcomes have yet to be reported.
Materials and Methods: KARMA is a non-interventional registry of Australian patients receiving first-line treatment with ribociclib and aromatase inhibitor (AI), obtained via a Medicine Access Program (MAP) for HR+, HER2- MBC. Outcomes were compared with the ribociclib/letrozole cohort in MONALEESA-2.
Results: Data from 160 patients at 17 sites was analysed. Median follow-up is 36.5 months. Compared to MONALEESA-2, patients were numerically younger (54.3 vs. 62 years), with higher rates of bone-only metastases (31% vs. 21%). A total of 63 of 160 (39%) patients remain on treatment. A total of 56% of patients had at least 1 dose reduction, with neutropenia (68%) and abnormal liver enzymes (17%) the most common reasons. A total of 17 of 160 (11%) discontinued treatment due to toxicity, with no treatment related deaths. Median PFS was not reached (95% CI 29.9- NR), with PFS at 12 months and 18 months being 76% and 67% respectively versus 25.3 months, 73% and 63% in MONALEESA-2.
Conclusion: The ribociclib and AI combination was well tolerated in this real-world setting. The KARMA registry cohort achieved a superior PFS (>36.5 months) to MONALEESA-2, potentially due to more favourable baseline disease characteristics. Less frequent assessment scheduling in this non trial setting may also contribute.
Competing Interests: Disclosure Vanessa Wong has received speaker honoraria from Amgen and Janssen, and her affiliated institution is the recipient of research grant funding from Pierre-Fabre, Amgen, Roche, MSD, AstraZeneca and Merck. Richard de Boer is on the Australian advisory board for Eli Lilly, Novartis and Pfizer, received speaker honoraria from Novartis and Eli Lilly, and research funding from Novartis and Pfizer. Katharine Cuff has received speaker honoraria from Novartis, is on the advisory board for Novartis, Pfizer and Ipsen, and is part of Amgen education support. Sheau Wen Lok's breast research team has received funding from Novartis, AstraZeneca, Roche and Amgen.
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