Background: Adjuvant trastuzumab trials in HER2+ breast cancer (BC) demonstrated a large reduction in recurrence and death. Central testing showed HER2 non-amplified participants derived similar benefit. Among HER2-amplified patients (pts), multiple studies showed no effect on benefit by degree of amplification. Blinded internal and external review confirmed the non-amplified nature of the HER2 normal group. Based on these findings, NSABP B-47, sponsored by the NCI, was activated January 2011 and is actively accruing. The study is NCI central IRB approved, open via the CTSU, and endorsed by SWOG, ECOG, and RTOG. Methods: Study: Chemotherapy treatment is by physician choice: The non-anthracycline regimen is TC (docetaxel 75 mg/m2, cyclophosphamide (C) 600 mg/m2) IV q 3 wks for 6 cycles; the anthracycline regimen is AC → WP (doxorubicin 60 mg/m2 and C 600 mg/m2 IV either q 3 wks or q 2 wks [investigator discretion] for 4 cycles → paclitaxel 80 mg/m2 IV wkly for 12 doses). Pts are randomly assigned to chemotherapy with or without trastuzumab for 1 year. Pts receive adjuvant radiation therapy and endocrine therapy, as clinically indicated. Detailed menstrual history, concurrent medications, weight changes, and biomarkers (estrogen, stress, inflammation), are being collected. Eligibility: Eligibility includes: node positive or high risk node negative BC pts; HER2 IHC 1+ or 2+ scores, but non amplified by FISH; normal cardiac, renal, and liver function. Detailed eligibility will be provided. Statistical Design: The primary aim is to determine whether the addition of trastuzumab to chemotherapy improves invasive disease-free survival (IDFS). 3,260 pts will be enrolled to provide statistical power of 0.9 to detect a 33% reduction in the hazard rate of IDFS using a one-sided alpha level of 0.025. Progress: Protocol was activated in January 2011. First pt was entered in February 2011. As of January 23, 2013, 1,416 of 3,260 (43.4 %) pts have been enrolled. Updated information on enrollment and study background will be provided. Support: NCI U10-12027, -37377, 69651, 69974, and Genentech, Inc. Clinical trial information: NCT01275677.