11167 Background: Cyclin-dependent kinase 4/6 inhibitors (CDK4/6i), including ribociclib and abemaciclib, are widely used in hormone receptor–positive, HER2-negative high-risk early-stage breast cancer in combination with endocrine therapy. While randomized trials have demonstrated survival benefits, comparative real-world outcomes between these agents remain limited. This study evaluates all-cause mortality among patients treated with ribociclib versus abemaciclib using a large real-world database. Methods: We conducted a retrospective cohort study using the TriNetX US Collaborative Network, a global federated health research network, including adult patients with breast cancer treated with ribociclib (n = 7,697) or abemaciclib (n = 12,626) within the past 20 years. Two cohorts were constructed and balanced using 1:1 propensity score matching (PSM) based on age at diagnosis, sex, and race. The primary outcome was all-cause mortality at 1, 3, and 5 years. Kaplan–Meier survival curves and Cox proportional hazards models were used to estimate survival probabilities and hazard ratios. Results: After PSM, a total of 15,374 patients were included (7,687 per cohort). Mean age was 60.2±13.5 years in the ribociclib cohort and 60.2±13.4 years in the abemaciclib cohort. Most patients were female (99%) and White (72%). At 1 year, survival probability for ribociclib was 91.5% compared with 89.0% for abemaciclib (hazard ratio 0.74, 95% CI 0.66–0.84; log-rank p < 0.001). There was no significant difference in survival probabilities at 3 years (70.1% vs 72.1%) or 5 years (56.6% vs 55.1%), with hazard ratios not significantly different from 1.0. Conclusions: In this real-world analysis, ribociclib use was associated with lower all-cause mortality at 1 year compared with abemaciclib; however, this difference did not persist at longer follow-up. These findings should be interpreted cautiously given potential residual confounding and differences in clinical indications between agents. Further studies accounting for disease stage and treatment context are warranted.
Okafor et al. (Wed,) studied this question.