 A pivotal trial that established the role of preoperative systemic therapy was the NSABP trial B-187. In this trial, women with localized breast cancer were randomized to receive Adriamycin, Cytoxan AC either preoperatively or postoperatively. There was no difference between the two groups in disease-free and overall survival. Furthermore, quantifying tumor response preoperatively allowed prediction of patient outcome in terms of disease-free and overall survival. Specifically, patients achieving a pathologic complete response, i.e., complete disappearance of invasive cancer on pathologic examination, had the best outcome, establishing the role of response as a valid surrogate predictor of the sensitivity of distant micrometastatic disease to chemotherapy and subsequent clinical outcome. In addition, breast-conserving surgery was more frequently performed in the preoperative treatment group, an advantage over the postoperative treatment approach. Most importantly, however, NSABP trial B-18 showed conclusively that primary systemic therapy is safe and does not place patients at a disadvantage by delaying primary surgical treatment. Another large, multicenter prospective trial conducted by the European Organization for Research and Treatment of Cancer EORTC confirmed the findings of NSABP trial B-18. 