The Hurria Older PatiEnts (HOPE) With Breast Cancer Study

The goal of this study is to develop a "bedside to bench" model of clinical and biological predictors for toxicity to adjuvant and neoadjuvant chemotherapy in older adults with breast cancer. The investigators will develop a predictive model using clinical and biological predictors of toxicity to adjuvant and neoadjuvant chemotherapy in older adults with breast cancer. The investigators will also determine the association between clinical and biological factors and reduced relative dose intensity of the prescribed chemotherapy regimen. In addition, the investigators will explore specific chemotherapy toxicities associated with reduced relative dose intensity of a prescribed regimen.