Prevalence and prognosis of patients with breast cancer eligible for adjuvant abemaciclib or ribociclib: a nationwide population-based study.

Liu, Xingrong; Binicy, Behnaz; Acs, Balazs; Eriksson Bergman, Louise; Loibl, Sibylle; Gnant, Michael; Untch, Michael; Valachis, Antonios et al. · Lancet Reg Health Eur · 2025

prospective_cohort · Level II

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Abstract

Nationwide studies on the prevalence, characteristics and long-term prognosis of patients with early breast cancer and a potential indication for adjuvant CDK4/6 inhibitors are lacking. We leveraged a prospectively collected nationwide cohort of all patients treated for breast cancer in Sweden in 2007-2023 and identified patients fulfilling the monarchE and/or the NATALEE eligibility criteria, to estimate the proportion of eligible patients for adjuvant CDK4/6 inhibitors and their outcomes. Overall survival (OS) was the primary endpoint of interest. In addition, we compared distant relapse-free survival and OS of a patient subset treated in the Stockholm-Gotland region in 2012-2020 to patients enrolled in the phase 3 PANTHER trial (NCT00798070) in 2007-2011, before and after alignment of key inclusion criteria. Of 52,602 patients with ER-positive, HER2-negative breast cancer, 9553 (18.2%) fulfilled both the monarchE and the NATALEE criteria, 9800 (18.6%) fulfilled the NATALEE criteria only and 745 patients (1.4%) fulfilled the monarchE criteria only. Median follow-up was 6.87 years. Ten-year OS rates were 65.7% (95% CI 65.3%-67.0%) for monarchE-eligible and 70.2% (95% CI 69.3%-71.1%) for NATALEE-eligible patients, and 84.0% (95% CI 83.4%-84.6%) for non-eligible, 75.5% (74.4$-76.7%) for NATALEE-only eligible and 64.3% (95% CI 62.9%-65.7%) for concordant eligible patients for both studies (p < 0.0001). Before alignment of inclusion criteria, patients treated within the PANTHER trial had improved outcomes compared to those treated in clinical routine. However, the differences in outcomes disappeared after alignment. These results inform on the prevalence and prognosis of candidates for adjuvant CDK4/6 inhibitors at a nationwide level. Cancerfonden, Bröstcancerförbundet, Radiumhemmets Forskningsfonder, Amgen, Roche, Sanofi-Aventis.