Multidisciplinary Practical Guidance for Implementing Adjuvant CDK4/6 Inhibitors for Patients with HR-Positive, HER2-Negative Early Breast Cancer in Canada

Abstract

Cyclin-dependent kinase (CDK)4/6 inhibitors have become a key component of adjuvant treatment for patients with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) early breast cancer who are at high risk of recurrence. The addition of abemaciclib and ribociclib to standard endocrine therapy has demonstrated clinically meaningful improvements in invasive disease-free survival, supported by the monarchE and NATALEE trials, respectively. With expansion of patient eligibility for CDK4/6 inhibitors, multidisciplinary coordination among medical oncologists, surgeons, nurses, pharmacists, and other health care providers is critical to optimizing patient identification, monitoring, and management of adverse events. This expert guidance document provides practical recommendations for implementing adjuvant CDK4/6 inhibitor therapy in routine clinical practice, incorporating insights from multiple specialties and with patient advocacy representation. Key considerations include patient selection based on clinical trial data, treatment duration, dosing schedules, adverse event profiles, monitoring requirements, drug-drug interactions, and patient-specific factors such as tolerability, cost, and quality of life. This guidance aims to support Canadian clinicians in effectively integrating CDK4/6 inhibitors into clinical practice, ensuring optimal patient outcomes through a multidisciplinary and patient-centric approach.

Keywords: CDK4/6 inhibitors; HR+, HER2− early breast cancer; adjuvant therapy; multidisciplinary care; practical recommendations.

Figure 1

Patient Inclusion Criteria for monarchE and NATALEE [31,43,44]. Green indicates patient eligibility and red indicates patient ineligibility. ECOG: Eastern Cooperative Oncology Group; ET: endocrine therapy; HER2: human epidermal growth factor receptor 2; HR: hormone receptor; mi: micrometastasis; PS: performance status. Green indicates part of inclusion criteria and red indicates not part of inclusion criteria.

Figure 2

Common Adverse Events (≥15%) from the monarchE and NATALEE Trials [19,20]. AE: adverse event.

Figure 3

Recommended Dose Holds for Abemaciclib and Ribociclib [32,33].

Figure 4

Monitoring Recommendations for Abemaciclib and Ribociclib [32,33]. CBC: complete blood count; ECG: electrocardiogram; ILD: interstitial lung disease; Q2W: every two weeks; QM: every month.