Ep. 1: Adjuvant Ribociclib in Early-Stage HR-Positive Breast Cancer: Clinical Insights
Key Points
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The NATALEE trial supports adjuvant ribociclib plus endocrine therapy for a broad population of early-stage hormone receptor (HR)–positive breast cancer patients, including select node-negative cases.
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Ribociclib dosing in the adjuvant setting is lower than in metastatic disease, which may improve tolerability while maintaining efficacy.
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Treatment selection between ribociclib and abemaciclib should be individualized, considering treatment duration, toxicity profile, and patient goals.
Integrating CDK4/6 Inhibitors in the Adjuvant Setting
Rahul Gosain, MD, MBA, of Wilmot Cancer Institute, and Rohit Gosain, MD, of Roswell Park Comprehensive Cancer Center, led a roundtable discussion on adjuvant therapy for HR-positive breast cancer at an event coinciding with the 2025 San Antonio Breast Cancer Symposium. The focus was on the role of CDK4/6 inhibitors, specifically ribociclib and abemaciclib, in combination with endocrine therapy. Joining them were panelists Sara Hurvitz, MD, FACP, of Fred Hutchinson Cancer Center; Sherry Shen, MD, of Memorial Sloan Kettering Cancer Center; and Eleonora Teplinsky, MD, of Valley-Mount Sinai Comprehensive Cancer Care.
CDK4/6 Inhibitor Trials and Patient Selection
The panel began by reviewing the NATALEE trial, which evaluated ribociclib in the adjuvant setting. This phase 3 trial enrolled more than 5,000 patients with stage II to III HR-positive breast cancer, including node-negative stage IIA patients with high-risk features such as grade 3 disease, high Ki-67, or elevated recurrence scores. The trial demonstrated that adding ribociclib to a nonsteroidal aromatase inhibitor significantly improved invasive and distant disease–free survival, with an approximate 30% relative reduction in recurrence risk compared with endocrine therapy alone.
Dr. Shen highlighted the broader eligibility criteria of NATALEE compared with the monarchE trial for abemaciclib, noting that NATALEE included patients with stages 2B and 3 disease, as well as select stage 2A patients based on risk factors. The ribociclib dosing in the adjuvant setting was lower (400 mg daily, 3 weeks on/1 week off) than in the metastatic setting (600 mg daily), potentially improving tolerability while maintaining efficacy.
Clinical Implications and Individualized Decision-Making
Dr. Teplinsky emphasized that the 4- and 5-year follow-up data demonstrate meaningful benefit even in select node-negative patients, providing clearer guidance for clinicians counseling patients. The discussion also focused on practical considerations, including management of adverse effects such as diarrhea, neutropenia, and rare hepatotoxicity, as well as differences in treatment duration (ribociclib for 3 years vs abemaciclib for 2 years). The experts underscored that selection between available CDK4/6 inhibitors should be individualized based on patient comorbidities, preferences, and tolerance for potential toxicities.