The CDK4/6 Inhibitor Dosing Knowledge (CDK) Study

Actively Recruiting

Phase 3

Age: 65Years +

All Genders

NCT06377852

The CDK4/6 Inhibitor Dosing Knowledge (CDK) Study

Led by American Society of Clinical Oncology · Updated on 2026-05-13

500

Participants Needed

Research Sites

200 weeks

Total Duration

AI-Summary

What this Trial Is About

The purpose of this study is to generate evidence on an alternative dosing strategy for CDK4/6 inhibitors to help more patients with Metastatic Breast Cancer (MBC) (age ≥ 65 years) tolerate side effects and stay on treatment longer, to derive the most clinical benefit from these drugs. The primary objective of the CDK Study is to compare time to treatment discontinuation (TTD) on the approved dosing for palbociclib (125 mg orally daily on days 1-21 of 28-day cycle) or ribociclib (600 mg orally daily on days 1-21 of 28-day cycle) vs. TTD using titrated dosing approach with the same schedule but starting at a lower dose of palbociclib (100 mg or 75 mg) or ribociclib (400 mg or 200 mg) and escalating the dose if well-tolerated in combination with provider/patient choice endocrine therapy (aromatase inhibitor (AI) or fulvestrant) in patients age 65 or older with HR+/HER2- MBC. The secondary and exploratory objectives will generate evidence needed to personalize treatment decisions by comparing patient-centric secondary outcomes and evaluating baseline factors. Together with their treating physician, participants will choose the CDK4/6 inhibitor (palbociclib or ribociclib) and which endocrine therapy (aromatase inhibitor or fulvestrant) of their choice but will be randomized to either Arm 1 (indicated dosing) or Arm 2 (titrated dosing). Note: Telehealth visits are allowed at any time per institutional guidelines. In addition, the study allows for remote consenting per institutional guidelines.

CONDITIONS

Official Title

The CDK4/6 Inhibitor Dosing Knowledge (CDK) Study

Who Can Participate

Age: 65Years +

All Genders

Eligibility Criteria

You may qualify if you...

Hormone receptor positive (HR+) HER2 negative metastatic breast cancer as per ASCO/CAP guidelines
Candidate for planned endocrine therapy combined with first use of palbociclib or ribociclib in metastatic setting
Age 65 years or older
Adequate bone marrow and organ function within specified laboratory limits or minor non-significant abnormalities
Absolute neutrophil count �3e�3d 1,000/�b5L
Total bilirubin �3c= 1.5 x institutional upper limit of normal (ULN), or up to 5x ULN if Gilbert's disease documented
AST/ALT �3c 3 x ULN, or �3c= 5 x ULN if metastatic liver disease documented
Baseline QTc �3c= 480 ms (for ribociclib patients only)
Ability to understand and willingness to provide informed consent, including remote consent

You will not qualify if you...

Previous treatment with a CDK4/6 inhibitor for metastatic breast cancer or within past 12 months in neo/adjuvant setting
Received more than 30 days of the planned endocrine therapy agent in metastatic setting at randomization
Known intolerance or allergy to planned study agents
Uncontrolled illness that would interfere with study compliance
Concurrent therapy with other investigational agents
Rapidly progressive brain metastases
Active or chronic Hepatitis B or C not meeting liver function criteria or on interacting medications
Use of drugs that prolong QT interval (for ribociclib patients) unless ECG monitoring is performed
Prior or concurrent malignancies undergoing active treatment

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