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. 2024 Aug 29:S1526-8209(24)00234-9.
doi: 10.1016/j.clbc.2024.08.022. Online ahead of print.

Real-World Analysis of Breast Cancer Patients Qualifying for Adjuvant CDK4/6 Inhibitors

Yada Kanjanapan  1 , Wayne Anderson  2 , Mirka Smith  2 , Jenny Green  2 , Elizabeth Chalker  3 , Paul Craft  4
Affiliations
Free article

Real-World Analysis of Breast Cancer Patients Qualifying for Adjuvant CDK4/6 Inhibitors

Yada Kanjanapan et al. Clin Breast Cancer. .
Free article

Abstract

Background: Adjuvant CDK4/6 inhibitors abemaciclib and ribociclib improved disease-free survival (DFS) added to endocrine therapy in hormone receptor (HR)-positive HER2-negative early breast cancer (EBC), in monarchE (NCT03155997) and NATALEE (NCT03701334) trials respectively. We assessed the proportion and outcome of EBC patients qualifying for adjuvant CDK4/6 inhibitors in the real-world.

Methods: Consecutive female patients with HR-positive HER2-negative EBC between 1997 and 2017 from the Australian Capital Territory and South-East New South Wales Breast Cancer Treatment Group registry were analyzed. Patients eligible for abemaciclib had ≥4 axillary nodes involved or 1-3 nodes plus primary >5 cm or grade 3. Ribociclib eligibility was defined as node-positive and node-negative with primary >5 cm or >2 cm grade 3.

Results: Of 3840 patients, 671 (17.5%) were abemaciclib-eligible and 1587 (41.3%) ribociclib-eligible . The 5-year DFS was 77% and 94% in abemaciclib-eligible and noneligible registry patients respectively (HR 2.6, 95% CI 2.26-3.05, P < .001). The 5-year DFS was 86% and 97% in ribociclib-eligible and noneligible registry patients respectively (HR 1.92, 95% CI 1.67-2.19, P < .001). Compared with monarchE trial patients, abemaciclib-eligible registry patients were older (median 55 years in registry vs. 51 years in trial), with lower nodal burden (≥4 nodes in 44% in registry vs. 60% in trial). There were more stage III cancers in NATALEE trial patients (60%) than ribociclib-eligible registry patients (24%).

Conclusions: Many women with EBC will qualify for adjuvant CDK4/6 inhibitors (17.5% abemaciclib, 41.3% ribociclib) with resource and workforce implications. In the real-world setting, a greater proportion of adjuvant CDK4/6-eligible patients have lower stage disease, therefore the absolute benefit from treatment may be smaller than estimated by the trials.

Keywords: Abemaciclib; Adjuvant therapy; Breast cancer; CDK4/6 inhibitors; Ribociclib.

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Conflict of interest statement

Disclosure YK: Advisory board- Novartis; Speaker's bureau- AstraZeneca, MSD, Novartis; Travel/accommodation- Pfizer, Lilly, BMS. The remaining authors have stated that they have no conflicts of interest.

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