PALbociclib CoLlaborative Adjuvant Study: A Randomized Phase III Trial of Palbociclib With Standard Adjuvant Endocrine Therapy Versus Standard Adjuvant Endocrine Therapy Alone for Hormone Receptor Positive (HR+) / Human Epidermal Growth Factor Receptor 2 (HER2)-Negative Early Breast Cancer

Inclusion Criteria
Premenopausal and postmenopausal women or men with Stage II or Stage III early invasive breast cancer
Patients with multicentric and/or multifocal and/or bilateral early invasive breast cancer whose histopathologically examined tumors all meet pathologic criteria for ER+ and/or PR+ and HER-\
Patients must have histologically confirmed hormone receptor positive (ER+ and/or PR+), HER2-, early invasive breast cancer
Patients must have undergone breast surgery for the current malignancy
A formalin-fixed paraffin-embedded tumor tissue block must be transmitted to a central sample repository and confirmation of receipt must be available prior to randomization
ECOG performance status 0-1
Patients must be able and willing to swallow and retain oral medication without a condition that would interfere with enteric absorption
Serum or urine pregnancy test must be negative within 7 days of randomization, in women of childbearing potential
Patients may or may not have received neo/adjuvant therapy, but must be after last dose of chemotherapy and/or biologic therapy and must have sufficient resolution of side effects per physician assessment at the time of randomization
Patients may or may not have received breast/axilla/post-mastectomy chest wall radiotherapy, but must be after last dose of radiotherapy and must have sufficient resolution of side effects per physician assessment at the time of randomization
Patients must have sufficient resolution of any surgical side effects from the last surgery per physician assessment, with no active wound healing complications at the time of randomization
Patients either must be initiating or have already started adjuvant hormonal treatment
Exclusion Criteria
Concurrent therapy with other Investigational Products
Prior therapy with any CDK inhibitor
Patients with Stage I or IV breast cancer
History of allergic reactions attributed to compounds of chemical or biologic composition similar to palbociclib
Patients receiving any medications or substances that are potent inhibitors or inducers of CYP3A isoenzymes within 7 days of randomization
Uncontrolled intercurrent illness that would limit compliance with study requirements
Pregnant women, or women of childbearing potential without a negative pregnancy test within 7 days prior to randomization
Patients with a history of any malignancy
Patients have previously received endocrine therapy within 5 years prior to diagnosis of the current malignancy
Patients on combination antiretroviral therapy
Patients with clinically significant history of any liver disease
Patients receiving concurrent exogenous hormone therapy