The main purpose of this study is to learn if the usual chemotherapy given before surgery (neoadjuvant therapy) for breast cancer plus the experimental drug, atezolizumab, is better than the usual chemotherapy plus a placebo. (A placebo is a drug that looks like the study drug but contains no medication.) The usual chemotherapy in this study is paclitaxel (WP) and carboplatin followed by doxorubicin and cyclophosphamide (AC) or epirubicin and cyclophosphamide (EC). Usually, after neoadjuvant therapy and surgery for triple negative breast cancer, no additional treatment is given unless the cancer returns. This study will also look at continuing treatment after surgery with atezolizumab or the placebo. To be better, atezolizumab given with the neoadjuvant therapy should be better at: 1) decreasing the amount of tumor in the breast than the placebo given with the usual chemotherapy and 2) decreasing the chance of the cancer from returning after surgery.

Another purpose of this study is to test the good and bad effects of atezolizumab when added to the usual chemotherapy. Atezolizumab may keep your cancer from growing but it can also cause side effects.