NCT06377852 · American Society of Clinical Oncology
The CDK4/6 Inhibitor Dosing Knowledge (CDK) Study
What this study 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.
View original scientific description
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.
Interventions
DRUG
Palbociclib 125mg
Arm 1: Indicated dosing for palbociclib (125 mg orally daily on days 1-21 of 28-day cycle)
DRUG
Ribociclib 600mg
Arm 1: Indicated dosing of ribociclib (600 mg orally daily on days 1-21 of 28-day cycle)
DRUG
Ribociclib
Arm 2: Titrated dosing approach with the same schedule but starting at a lower dose of ribociclib (400 mg or 200 mg) and escalating the dose if well-tolerated in combination with provider/patient choice of endocrine therapy.
DRUG
Palbociclib
Arm 2: Titrated dosing approach with the same schedule but starting at a lower dose of palbociclib (100 mg or 75 mg) and escalating the dose if well-tolerated in combination with provider/patient choice of endocrine therapy.
Primary outcome measures
Time to Treatment Discontinuation (TTD)
Time frame: up to 48 months
Our primary outcome is time to CDK4/6 inhibitor discontinuation (TTD): the number of days between randomization and the last day the patient takes any dose of the same CDK4/6 inhibitor (regardless of drug holds, dose changes
Who can participate
This study lists these criteria on ClinicalTrials.gov. A study coordinator reviews eligibility during screening — this page does not determine whether you qualify.
Inclusion criteria
- Hormone receptor positive (HR+) HER2 negative metastatic breast cancer. Cut-off values for positive/negative staining should be as per standard practice in accordance with ASCO/CAP (American Society of Clinical Oncology/College of American Pathologists) guidelines. Verification of histology is preferred at the time of recurrence and where not possible or necessary in the judgment of the treating physician, the study will accept histology from the initial diagnosis. 2. Candidate for planned endocrine therapy in combination with 1st use of palbociclib or ribociclib, in the metastatic setting. The planned endocrine partner can be an aromatase inhibitor (letrozole, anastrozole, exemestane) or fulvestrant, selected through patient/provider choice. 3. Aged 65 years or older 4. Adequate bone marrow and organ function. Laboratory values must be within normal institutional limits, or within ranges as indicated below, or demonstrate minor abnormalities that are deemed cli
Where
- Chandler, Arizona
- Gilbert, Arizona
- Glendale, Arizona
- Goodyear, Arizona
- Mesa, Arizona
- Phoenix, Arizona
- Scottsdale, Arizona
- Aurora, Colorado
- Denver, Colorado
- Highlands Ranch, Colorado
- Derby, Connecticut
- Fairfield, Connecticut
And 51 more locations — see the full list below.
Collaborators
Patient-Centered Outcomes Research Institute
Related conditions & keywords
Frequently asked questions
What is a clinical trial?
A clinical trial is a research study that tests new medical treatments, drugs, devices, or procedures to determine their safety and effectiveness. Trials are carefully designed and monitored to protect participants while advancing medical knowledge.
Is it safe to participate?
Clinical trials follow strict safety guidelines and ethical standards. Trials must be reviewed and approved, and participants are closely monitored by medical professionals throughout the study. You can withdraw at any time if you choose.
Will I be compensated?
Many clinical trials offer compensation for your time, travel expenses, and inconvenience. The specific compensation varies by study and will be discussed during the screening process. All study-related medical care is typically provided at no cost to participants.
Will I receive a placebo instead of treatment?
When effective treatment exists, participants typically receive either the standard treatment plus the study intervention, or the standard treatment plus placebo. You would not be denied effective care. Placebos are primarily used when no proven treatment is available, or in addition to standard care. Your trial consent form will clearly explain what treatments you may receive.
Can I leave a trial if I change my mind?
Absolutely. Participation in clinical trials is completely voluntary. You have the right to withdraw from the study at any time, for any reason, without penalty or loss of benefits to which you are otherwise entitled.
How long does a clinical trial last?
Trial duration varies widely depending on the study design and purpose. Some trials last just a few weeks, while others may continue for months or years. The study coordinator will provide specific timeline information during your screening call.
Data: ClinicalTrials.gov · synced Jun 29, 2026 · Source of record for eligibility and locations