ArticleBreast cancer (Tokyo, Japan)2026
Target trial emulation of first-line ribociclib versus palbociclib in hormone receptor-positive, HER2-negative metastatic breast cancer: a comparative effectiveness study.
Article in Breast cancer (Tokyo, Japan), 2026. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Not yet cited in PubMed.
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Abstract
backgroundHead-to-head randomized trials of CDK4/6 inhibitors are lacking. We emulated a target trial of first-line ribociclib versus palbociclib in hormone receptor-positive, HER2-negative metastatic breast cancer.
methodsUsing TriNetX (January 2014-March 2025), adults initiating first-line endocrine therapy plus ribociclib or palbociclib underwent 1:1 propensity score matching. The primary outcome was all-cause mortality. The co-primary calendar-restricted survival analysis applied a year-level restriction beginning January 1, 2017, the calendar year of ribociclib market entry.
resultsThe prescription-confirmed cohort comprised 11,685 patients; 4394 were matched (2197 per group; mean age 60.2 years; 97.9% female). In the whole-period co-primary analysis, ribociclib was associated with longer overall survival (hazard ratio [HR] 0.82, 95% CI 0.73-0.92) and a 48-month restricted mean survival difference of 1.7 months (95% CI 0.5-2.8). The all-initiator analysis removing the second-prescription requirement yielded HR 0.86 (95% CI 0.75-0.99) but did not restrict calendar time. The separately matched calendar-restricted co-primary analysis (from 2017; 1924 per arm) yielded HR 0.90 (95% CI 0.82-0.99); residual temporal confounding could favor ribociclib. Exploratory analyses showed lower cause-specific hazards of recorded hematologic events (neutropenia HR 0.69, thrombocytopenia HR 0.52, anemia HR 0.80) and higher hazards of recorded QT prolongation and dermatologic events (HR 1.61 and 1.41); no detectable differences were observed for healthcare utilization or severe infections.
conclusionsBoth co-primary analyses showed an association with longer overall survival for ribociclib, with attenuation in the calendar-restricted analysis (HR 0.90, 95% CI 0.82-0.99). These findings are hypothesis-generating, not evidence of superiority, and require randomized confirmation.
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