Pathobiology of preoperative chemotherapy: findings from the National Surgical Adjuvant Breast and Bowel (NSABP) protocol B-18.

Background: Examination was performed on pathologic material from patients enrolled in the National Surgical Adjuvant Breast Project (NSABP) protocol B-18, in which the clinical effects of preoperative (preop) and postoperative (postop) doxorubicin and cyclophosphamide (AC) were compared.

Methods: Of the total number of 1523 patients, 1234 patients (81%) were in the pathologically evaluable cohort. Six hundred twenty-six patients had been randomized prospectively to receive AC postop and 608 had been randomized to receive AC preop.