# Characteristics of Patients With Hormone Receptor-Positive/Human Epidermal Growth Factor Receptor 2-Negative Early Breast Cancer Eligible for Adjuvant Cyclin-Dependent Kinase 4/6 (CDK4/6) Inhibitors: Real-Life Evidence in a Colombian Cancer Center

## TL;DR

This study examines which early breast cancer patients in Colombia are eligible for CDK4/6 inhibitors, showing that many qualify, especially those with advanced disease.

## Contribution

The study provides real-world evidence on CDK4/6 inhibitor eligibility in a Latin American population, highlighting demographic and clinical differences from clinical trials.

## Key findings

- 36.2% of patients were eligible for abemaciclib, often due to high nodal involvement or other high-risk features.
- 59% of patients were eligible for ribociclib, with a significant portion having stage III disease.
- The Colombian cohort was older and had fewer grade 3 tumors compared to pivotal trial populations.

## Abstract

Background

The introduction of cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) in the adjuvant setting for hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-) early breast cancer (BC) has expanded treatment options for high-risk patients. However, real-world data on eligibility for these therapies in Latin American populations remain limited.

Methods

This retrospective study analyzed 334 patients with HR+/HER2- early breast cancer (stages I-III) treated at a Colombian cancer center (2022-2024). Eligibility criteria for adjuvant abemaciclib (monarchE) and ribociclib (NATALEE) trials were applied. Clinicopathological characteristics and treatment patterns were assessed.

Results

Among abemaciclib-eligible patients (36.2%, n=121), 54.5% had ≥4 positive nodes, and 45.5% met alternative high-risk criteria (1-3 nodes plus tumor size of ≥5 cm or grade 3 or Ki-67 of ≥20%). Ribociclib-eligible patients (59%, n=197) included 53.8% with stage III disease and 12.7% with node-negative, grade 3 tumors. Descriptive comparison with pivotal trials shows that compared to pivotal trials, our cohort had an older median age (61 versus 51-52 years) and a lower prevalence of grade 3 tumors (17.1% versus 30%-40%).

Conclusion

A substantial proportion of Colombian patients with HR+/HER2- early breast cancer qualify for adjuvant CDK4/6i, particularly those with nodal involvement. These findings highlight both the clinical opportunity and economic challenges of implementing these therapies in resource-limited settings while underscoring the need for improved early detection to reduce advanced presentations. Eligibility based on clinical-pathological criteria identifies a high-risk group, though optimal selection may require biomarker refinement where available.