ERBB2 and breast cancer: Trastuzumab was then FDA approved in 2006 in the adjuvant setting for early-stage HER2-positive breast cancer after a joint analysis of two phase 3 trials comparing adjuvant CT with or without 52 weeks of trastuzumab (NSABP trial B-31 and NCCTG trial N9831). The CT backbone was four cycles of doxorubicin and cyclophosphamide followed by paclitaxel for 12 weeks (AC-T).