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RECRUITING Phase 3 ClinicalTrials.gov

The CDK4/6 Inhibitor Dosing Knowledge (CDK) Study

Sponsor: American Society of Clinical Oncology • ClinicalTrials.gov ID: NCT06377852

Registry updated: 2026-10-06
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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 ≥ 60 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 60 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.

Interventions

  • Palbociclib 125mg (Drug)
    Arm 1: Indicated dosing for palbociclib (125 mg orally daily on days 1-21 of 28-day cycle)
  • Ribociclib 600mg (Drug)
    Arm 1: Indicated dosing of ribociclib (600 mg orally daily on days 1-21 of 28-day cycle)
  • Ribociclib (Drug)
    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.
  • Palbociclib (Drug)
    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.

Eligibility criteria

Inclusion Criteria: 1. 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 60 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 clinically non-significant by the investigator. * Absolute neutrophil count ≥ 1,000/µL * Total bilirubin ≤ 1.5 x institutional upper limit of normal (ULN) (participants with documented Gilbert's disease are allowed total bilirubin up to 5X ULN) * AST (SGOT)/ALT (SGPT) \<3 x institutional ULN, or ≤ 5 x ULN for subjects with documented metastatic disease to the liver. 5. Baseline QTc ≤ 480 ms (only for ribociclib patients) 6. Ability to understand and the willingness to provide informed consent. Note: Remote consent is allowed per institutional guidelines. Exclusion Criteria: 1. Previous treatment with a CDK4/6 inhibitor for metastatic breast cancer, or previous treatment within the past 12 months with a CDK4/6 inhibitor in the neo/adjuvant breast cancer setting. 2. Received greater than 60 days (in the metastatic setting) of the specific endocrine therapy agent planned as partner to the CDK4/6 inhibitor in the study at the time of randomization. 3. Known history of intolerance or allergy to the planned agents used in this trial. 4. Uncontrolled intercurrent illness that, as evaluated by the treating clinician, would hinder compliance with study requirements. 5. Concurrent therapy with other investigational agents or anticancer therapy beyond aromatase inhibitors or fulvestrant. Note: radiation is allowed at any time. 6. Rapidly progressive brain metastases. Note: only applies to patients with known brain metastases. Brain imaging not required for enrollment. 7. Active or chronic Hepatitis B or C are eligible provided they meet liver function laboratory criteria and are not on medication with a known interaction with the study agents. 8. Current use of drugs that have known potential to prolong the QT interval (e.g., antiarrhythmic drugs), for patients on ribociclib. Note: If concomitant use cannot be avoided, monitor ECG when initiating, during concomitant use, and as clinically indicated. Refer to crediblemeds.org as a resource. 9. Prior or concurrent malignancies that are undergoing active treatment.

Conditions

Metastatic Breast Cancer

Locations

  • Ironwood Cancer & Research Centers — Chandler, Arizona, United States
  • Ironwood Cancer & Research Centers — Gilbert, Arizona, United States
  • Ironwood Cancer & Research Centers — Glendale, Arizona, United States
  • Ironwood Cancer & Research Centers — Goodyear, Arizona, United States
  • Ironwood Cancer & Research Centers — Mesa, Arizona, United States
  • Ironwood Cancer & Research Centers — Mesa, Arizona, United States
  • Ironwood Cancer & Research Centers — Phoenix, Arizona, United States
  • Ironwood Cancer & Research Centers — Scottsdale, Arizona, United States
  • Providence Medical Foundation — Eureka, California, United States
  • Providence Medical Foundation — Santa Rosa, California, United States
  • University of Colorado Anschutz Medical Campus — Aurora, Colorado, United States
  • UCHealth Cherry Creek Medical Center — Denver, Colorado, United States
  • UCHealth Highlands Ranch Hospital — Highlands Ranch, Colorado, United States
  • Smilow Cancer Hospital Care Center - Derby — Derby, Connecticut, United States
  • Smilow Cancer Hospital Care Center - Fairfield — Fairfield, Connecticut, United States
  • Smilow Cancer Hospital at Glastonbury — Glastonbury, Connecticut, United States
  • Smilow Cancer Hospital Care Center - Greenwich — Greenwich, Connecticut, United States
  • Smilow Cancer Hospital Care Center - Guilford — Guilford, Connecticut, United States
  • Smilow Cancer Hospital at Saint Francis — Hartford, Connecticut, United States
  • Smilow Cancer Hospital - Yale New Haven Health — New Haven, Connecticut, United States
  • Yale University/Yale Cancer Center/Yale School of Medicine — New Haven, Connecticut, United States
  • Smilow Cancer Hospital Care Center - North Haven — North Haven, Connecticut, United States
  • Smilow Cancer Hospital Care Center - Torrington — Torrington, Connecticut, United States
  • Smilow Cancer Hospital Care Center - Trumbull — Trumbull, Connecticut, United States
  • Smilow Cancer Hospital Care Center - Waterbury — Waterbury, Connecticut, United States
  • Smilow Cancer Hospital - Waterford — Waterford, Connecticut, United States
  • Miami Cancer Institute — Miami, Florida, United States
  • Miami Cancer Institute — Plantation, Florida, United States
  • Emory University Winship Cancer Institute — Atlanta, Georgia, United States
  • Liberty County Cancer Care — Hinesville, Georgia, United States
  • Pembroke Medical Oncology & St Joseph's/Candler Oncology Infusion Suite — Pembroke, Georgia, United States
  • Lewis Cancer and Research Pavilion — Savannah, Georgia, United States
  • Candler Medical Oncology Practice and Infusion — Statesboro, Georgia, United States
  • Northwest Cancer Center — Crown Point, Indiana, United States
  • Northwest Cancer Center-Dyer — Dyer, Indiana, United States
  • St. Mary Medical Center — Hobart, Indiana, United States
  • Powers Health Cancer Research Foundation — Munster, Indiana, United States
  • Northwest Cancer Center — Valparaiso, Indiana, United States
  • The University of Kansas Cancer Center — Westwood, Kansas, United States
  • The Jackson Laboratory (JAX) - Harold Alfond Center for Cancer Care — Augusta, Maine, United States
  • The Jackson Laboratory (JAX) - Northern Light Cancer Care — Brewer, Maine, United States
  • Dana-Farber Cancer Institute — Boston, Massachusetts, United States
  • Dana-Farber Brigham Cancer Center Foxborough — Foxborough, Massachusetts, United States
  • Dana-Farber Cancer Institute Merrimack Valley — Methuen, Massachusetts, United States
  • Dana-Farber Brigham Cancer Center at Milford Regional Medical Center — Milford, Massachusetts, United States
  • Dana-Farber Brigham Cancer Center at South Shore Health — Weymouth, Massachusetts, United States
  • Dana-Farber/New Hampshire Oncology-Hematology — Londonderry, New Hampshire, United States
  • Englewood Hospital — Englewood, New Jersey, United States
  • Capital Health Medical Center - Hopewell — Pennington, New Jersey, United States
  • Penn Medicine - Princeton Health — Plainsboro, New Jersey, United States
  • Lovelace Medical Center - Saint Joseph Square — Albuquerque, New Mexico, United States
  • Lovelace Women's Hospital — Albuquerque, New Mexico, United States
  • Presbyterian Kaseman Hospital — Albuquerque, New Mexico, United States
  • The University of New Mexico Comprehensive Cancer Center — Albuquerque, New Mexico, United States
  • Memorial Medical Center — Las Cruces, New Mexico, United States
  • Presbyterian Rust Medical Center/Jorgensen Cancer Center — Rio Rancho, New Mexico, United States
  • Levine Cancer Institute — Albemarle, North Carolina, United States
  • Levine Cancer Institute — Charlotte, North Carolina, United States
  • Levine Cancer Institute — Charlotte, North Carolina, United States
  • Levine Cancer Institute — Charlotte, North Carolina, United States
  • Levine Cancer Institute — Charlotte, North Carolina, United States
  • Levine Cancer Institute — Charlotte, North Carolina, United States
  • Levine Cancer Institute — Concord, North Carolina, United States
  • Levine Cancer Institute — Forest City, North Carolina, United States
  • Levine Cancer Institute — Gastonia, North Carolina, United States
  • Levine Cancer Institute — Huntersville, North Carolina, United States
  • Levine Cancer Institute — Lincolnton, North Carolina, United States
  • Levine Cancer Institute — Matthews, North Carolina, United States
  • Levine Cancer Institute — Monroe, North Carolina, United States
  • Levine Cancer Institute — Shelby, North Carolina, United States
  • University of Cincinnati Medical Center — Cincinnati, Ohio, United States
  • University of Cincinnati Medical Center - West Chester Hospital — West Chester, Ohio, United States
  • Penn Medicine - Lancaster General Hospital — Lancaster, Pennsylvania, United States
  • Capital Health Hematology Oncology Specialists — Newton, Pennsylvania, United States
  • Penn Medicine - Perelman Center for Advanced Medicine — Philadelphia, Pennsylvania, United States
  • Penn Medicine - Pennsylvania Hospital — Philidelphia, Pennsylvania, United States
  • Penn Medicine - Chester County Hospital — West Chester, Pennsylvania, United States
  • Smilow Cancer Hospital - Westerly — Westerly, Rhode Island, United States
  • St. Joseph's Candler Bluffton Campus — Bluffton, South Carolina, United States
  • SC Cancer Specialists - Hilton Head at St. Joseph's/Candler — Hilton Head Island, South Carolina, United States
  • Levine Cancer Institute — Rock Hill, South Carolina, United States
  • Baptist Memorial Healthcare — Memphis, Tennessee, United States
  • Northwest Medical Specialties — Bonney Lake, Washington, United States
  • Northwest Medical Specialties — Federal Way, Washington, United States
  • Northwest Medical Specialties — Gig Harbor, Washington, United States
  • Northwest Medical Specialties — Olympia, Washington, United States
  • Northwest Medical Specialties — Puyallup, Washington, United States
  • Northwest Medical Specialties — Tacoma, Washington, United States
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Official Source

Data sourced from ClinicalTrials.gov, a service of the U.S. National Institutes of Health.

View Official Record