ARM II: Patients receive same therapy as in Arm I, except for additional trastuzumab (Herceptin) IV weekly beginning within 3 weeks following completion of chemotherapy and local therapy and continuing for 1 year. ER and/or PR positive patients receive tamoxifen as in Arm I but may be concurrent with trastuzumab (Herceptin). Following completion of doxorubicin and cyclophosphamide, post lumpectomy and post mastectomy patients may receive local radiotherapy daily for 5-6 weeks. Treatment continues in the absence of disease progression or unacceptable toxicity.