Adding an Immunotherapy Drug, MEDI4736 (Durvalumab), to the Usual Chemotherapy Treatment (Paclitaxel, Cyclophosphamide, and Doxorubicin) for Stage II-III Breast Cancer

Inclusion Criteria: * STEP 1: REGISTRATION (SCREENING): Participants must have histologically confirmed estrogen receptor (ER) positive and/or progesterone receptor (PR) positive (hormone receptor positive) and HER2 negative breast cancer, as per American Society of Clinical Oncology (ASCO) College of American Pathologists (CAP) guidelines * NOTE: Participants with HER2 positive disease by ASCO CAP guidelines are ineligible. HER2 negative and HER2 low or equivocal cases as per ASCO CAP guidelines that do not receive HER2 targeted therapy are eligible * STEP 1: REGISTRATION (SCREENING): Participants must have clinical stage II or III breast cancer * NOTE: Participants with inflammatory breast cancer are eligible * NOTE: Participants with occult (i.e. undetectable) primary breast cancer with axillary nodal involvement are not eligible, as MammaPrint testing has not been validated on tissue obtained from an axillary lymph node * STEP 1: REGISTRATION (SCREENING): Participants must not have metastatic disease (i.e., must be clinically M0 or Mx) Systemic staging studies with imaging should follow routine practice as per National Comprehensive Cancer Network (NCCN) and ASCO guidelines * STEP 1: REGISTRATION (SCREENING): Participants must not have locally recurrent breast cancer * STEP 1: REGISTRATION (SCREENING): Participants with multifocal disease in the same breast or synchronous bilateral primary tumors are eligible, however, all tumors that are biopsied must be hormone…