- Prior Therapy - Phase 1: Must be candidates to receive paclitaxel chemotherapy in combination with trastuzumab and pertuzumab. Phase 2: No prior chemotherapy, radiation, or definitive therapeutic surgery (e.g., mastectomy, lumpectomy or axillary dissection) for this malignancy. Patients who have had a prior sentinel lymph node biopsy for this malignancy are eligible. Patients who received equal to or less than 1 cycle of therapy (up to 4 weeks) will be allowed to enroll in this trial.