In a 4-year analysis of the NATALEE trial, adjuvant ribociclib plus NSAI continued to provide invasive disease-free survival benefit over NSAI alone in patients with hormone receptor–positive/ERBB2-negative early breast cancer, with stable safety outcomes observed.

This exploratory 4-year analysis demonstrated a consistent iDFS benefit with ribociclib plus NSAI with additional follow-up, with a 28.5% reduction in the risk of recurrence over NSAI alone and confidence intervals that continue to narrow. The absolute improvement in iDFS with ribociclib plus NSAI continued to increase from 2.7% at 3 years to 4.9% at 4 years. The iDFS, DDFS, RFS, and DRFS benefits were observed with ribociclib plus NSAI over NSAI alone beyond the planned 3-year ribociclib treatment duration, as all patients were no longer receiving ribociclib treatment at the data cutoff. A sustained iDFS benefit with ribociclib plus NSAI was seen across subgroups, including anatomic stage and nodal status, with a consistent reduction in risk of distant recurrences across subgroups. The safety profile remained unchanged with additional follow-up.

In prior analyses, an iDFS benefit was observed with ribociclib plus NSAI over NSAI alone.^10,21 However, at the time of those analyses, all patients had not yet discontinued ribociclib treatment (54.0% in the second interim efficacy analysis and 78.3% in the protocol-specified final analysis were no longer receiving treatment).^10,21 Thus, the efficacy of ribociclib beyond the planned treatment period was unknown. In this analysis, all patients had stopped ribociclib treatment, with 62.8% of patients having completed the planned 3-year treatment duration. At 4 years, the absolute improvement in iDFS increased and the Kaplan-Meier curves continue to separate with additional follow-up, suggesting a persistent benefit of adjuvant ribociclib beyond the planned 3-year treatment duration.

An iDFS benefit was observed with ribociclib plus NSAI over NSAI alone in patients with high-risk N0 disease. While this subgroup of patients in NATALEE do not have nodal involvement, enrolled patients with stage IIA node-negative (T2N0) disease were required to have additional high-risk features, including grade 3 disease or grade 2 disease with Ki-67 20% or higher or high genomic risk. Previous meta-analyses and population-based studies have shown risk of recurrence across patients with and without nodal involvement; however, many of the patient samples in these studies were enrolled decades prior to the follow-up analyses.^{5, 24} The cohorts in these long-term studies may not be reflective of contemporary treatment standards, which has the potential to overinflate the recurrence risk among some subgroups.