Adjuvant Paclitaxel and Trastuzumab for Node-Negative HER2-Positive Breast Cancer

* Participants will enroll in this study at the time they are starting their adjuvant therapy for breast cancer. Participants will receive chemotherapy with paclitaxel every week for 12 weeks. They will begin to receive trastuzumab at the same time they begin paclitaxel. Once they have completed the 12 weeks of paclitaxel and trastuzumab, they will receive trastuzumab every 3 weeks or weekly for 40 weeks. * Participants will be followed with routine assessments such as physical exam and vital signs every 3 months for the first year, and then every 6 months for years 2-5. Then we would like to keep track of the participants medical condition by calling them on the telephone once per year.