ARM II*: Patients receive doxorubicin hydrochloride, cyclophosphamide, and paclitaxel as in arm I. Patients then receive trastuzumab IV over 30-90 minutes beginning on day 1 of week 25 and continuing weekly for 52 courses in the absence of disease progression or unacceptable toxicity. NOTE: *Patients who completed paclitaxel on or after October 25, 2004 may receive trastuzumab for a maximum of 52 weeks either concurrently with paclitaxel or following completion of paclitaxel treatment.