≥ 18 years of age;

Histologically confirmed Stage I-IV breast cancer;

ECOG Performance Status 0-3;

Scheduled to start a new course of chemotherapy in the neo-adjuvant, adjuvant or metastatic setting for newly diagnosed or recurrent disease;

Growth factors, e.g., filgrastim, pegfilgrastim, are allowed, but their dose and duration will be tracked.

Absolute Lymphocyte Count (ALC) \> 500 cells/μL as determined by routine CBC with differential;

Signed, IRB approved written informed consent.

Study of the P16 Gene as a Predictor of Myelosuppression in Breast Cancer Patients