Inclusion Criteria: - Completed T-DM1 treatment on the parent study or who continue to receive T-DM1 at the time of the parent study closure - Expectation by the investigator that the patient may continue to benefit from additional T-DM1 treatment - For women of childbearing potential, agreement to use an effective form of contraception (patient and/or partner, e.g., surgical sterilization, a reliable barrier method, birth control pills, or contraceptive hormone implants) and to continue its use for the duration of the study. For men, agreement to use an effective form of contraception and to continue its use for the duration of the study. Exclusion Criteria: - Adverse events leading to T-DM1 discontinuation in the parent study - Ongoing serious adverse events from the parent study - Progressive disease during parent study or before starting the extension study - Peripheral neuropathy of Grade ≥ 3 per National Cancer Institute Common Terminology Criteria for Adverse Events (NCI CTCAE), Version 3.0 - History of symptomatic congestive heart failure ([CHF]; New York Heart Association [NYHA] Classes II-IV), ventricular arrhythmia requiring treatment, or history of myocardial infarction within 6 months prior to study entry - Severe dyspnea at rest due to complications of advanced malignancy or current requirement for continuous oxygen therapy - Current severe, uncontrolled systemic disease - Major surgical procedure or significant traumatic injury within 28 days prior to study entry or anticipation of the need for major surgery during the course of study treatment - Current pregnancy or lactation - History of receiving any investigational treatment or other systemic therapy directed at controlling cancer (i.e., chemotherapy, Herceptin�) since the patient's last dose in the parent study - History of hypersensitivity with previous T-DM1 treatment, precluding further dosing - Assessed by the investigator to be unable or unwilling to comply with the requirements of the protocol