Palbociclib / Letrozole or Fulvestrant in African American Women With HR+ HER2- Breast Cancer

The study is designed to assess the rate of completion of planned oncology therapy in the absence of a hematological event defined as episodes of febrile neutropenia and treatment discontinuation due to neutropenia. A completion rate of 80% is considered of clinical relevance as to benefit breast cancer patients who are at a higher risk of having ethnic neutropenia where as a completion rate of 60% is considered poor and to justify additional safety studies. A two stage design with a total of 35 patients is used to test if the completion rate is at least 80% versus if it is below 60% with 80% power at a significance level of 5%.

An exact confidence interval of the completion rate will be calculated. Investigators estimate there will be no more than a 10% rate of febrile neutropenia. Due to the small sample size, the analysis of secondary endpoints will be descriptive and will not include specific hypothesis testing.

Inclusion criteria

• Self-identified Black, African or African American women of ≥ 18 years of age with proven diagnosis of advanced adenocarcinoma of the breast (locoregionally recurrent or metastatic disease)
• ER-positive and/or PgR-positive tumor based on local laboratory results
• HER2-negative breast cancer based on local laboratory results (test to be used as per local practice)
• Patients must be appropriate candidates for letrozole or fulvestrant therapy
• Eastern Cooperative Oncology Group (ECOG) performance status 0-2
• Adequate bone marrow function:

• Absolute Neutrophil Count (ANC) ≥ 1,000/mm3 (1.0 x 109/L);
• Platelets ≥100,000/mm3 (100 x 109/L);
• Hemoglobin ≥9 g/dL (90 g/L).

Exclusion criteria

• Current use of food or drugs known to be potent inhibitors or inducers of CYP3A4
• Active uncontrolled or symptomatic brain metastases. Previously treated and clinically stable, as per Investigator's judgment, brain metastases are permitted.
• Previous CDK4/6 inhibitor

-