Statement: Participants in the primary trial must be willing to undergo anthracycline-based chemotherapy, or have previously received either cyclophosphamide or epirubicin.
Primary_evidence: Inclusion Criteria:   Adult patients  18 years of age.   Locally advanced, inflammatory, or early stage, unilateral, and histologically confirmed invasive breast cancer documented at a local laboratory (patients with inflammatory breast cancer must be able to have a core needle biopsy).   Herceptin (HER)2-positive tumor, confirmed by central testing using immunohistochemistry (IHC) and in situ hybridization (ISH) methods.   Willingness to receive anthracycline-based chemotherapy or have received doxorubicin/cyclophosphamide (AC) OR 5-fluorouracil (FU)/epirubicin/ cyclophosphamide (FEC) in a similar dose and schedule as described in the protocol as part of neoadjuvant or adjuvant treatment.   For women of childbearing potential and men with partners of childbearing potential, agreement to use a highly effective, non-hormonal form of contraception or 2 effective forms of non-hormonal contraception by the patient and/or partner. Contraception use must continue for the duration of study treatment and for at least 6 months after the last dose of study treatment. Male patients should use condoms for the duration of the study. Specific country requirements will be followed.   Negative results of serum pregnancy test for premenopausal women of reproductive capacity and for women < 12 months after menopause.   Patients may enroll before or after AC/FEC chemotherapy has completed.   Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.   Adequate hematologic, biochemistry, and cardiac assessments. Exclusion Criteria:   Stage IV breast cancer or bilateral breast cancer.   Pregnant or breastfeeding women.   History of other malignancy within the previous 5 years, except contralateral breast cancer and ductal carcinoma in situ (DCIS)/lobular carcinoma in situ (LCIS), appropriately treated carcinoma in situ of the cervix, non-melanoma skin carcinoma, Stage I uterine cancer, or other cancers with outcome similar to those mentioned above.   Radiation therapy, immunotherapy, or biotherapy within 5 years before study enrollment; non-cardiotoxic chemotherapy for malignancy treated > 5 years before study enrollment is allowed. Patients receiving AC/FEC in a similar fashion to the study treatment prescribed for adjuvant or neoadjuvant treatment of breast cancer will be allowed to enroll in the study after the completion of their AC/FEC. No other prior history of cardiotoxic chemotherapy is allowed.   Active cardiac history.   Current chronic daily treatment with oral corticosteroids or equivalent.   Patients with severe dyspnea at rest or requiring supplementary oxygen therapy.   Active, unresolved infections at screening.   Human immunodeficiency virus (HIV), hepatitis B virus (HBV), or hepatitis C virus (HCV) infection.   Major surgery within 4 weeks before enrollment that is unrelated to the breast cancer.   Patients for whom concomitant radiotherapy + T-DM1 may be contraindicated yet radiation therapy is planned.   Known hypersensitivity to any of the study drugs or derivatives, including murine proteins.   Grade  2 peripheral neuropathy at Baseline.