Statement: Patients with incurable and unresectable Breast Cancer are eligible for the primary trial, unless it is metastatic.
Primary_evidence: Inclusion Criteria:   HER2-positive disease determined locally   Histologically or cytologically confirmed invasive breast cancer   Prior treatment for breast cancer in the adjuvant, unresectable, locally advanced or metastatic setting must include both chemotherapy, alone or in combination with another agent, and an anti-HER2 agent, alone or in combination with another agent   Documented progression of incurable, unresectable, LABC, or mBC, defined by the investigator: progression must occur during or after most recent treatment for LABC/mBC or within 6 months of completing adjuvant therapy   Measurable and/or non-measurable disease   Left ventricular ejection fraction (LVEF) >/=50% by either echocardiogram (ECHO) or multiple-gated acquisition scan (MUGA)   Eastern Cooperative Oncology Group (ECOG) performance status of 0,1 or 2   Adequate organ function   Use of highly effective contraception as defined by the protocol Exclusion Criteria:   History of treatment with trastuzumab emtansine   Prior enrollment into a clinical study containing trastuzumab emtansine regardless of having received trastuzumab emtansine or not   Peripheral neuropathy of Grade >/= 3 per National Cancer Institute (NCI) common terminology criteria for adverse events (CTCAE) v 4.0   History of other malignancy within the previous 5 years, except for appropriately treated carcinoma in situ of the cervix, non-melanoma skin carcinoma, Stage 1 uterine cancer, synchronous or previously diagnosed HER2-positive breast cancer   History of receiving any anti-cancer drug/biologic or investigational treatment within 21 days prior to first study treatment except hormone therapy, which can be given up to 7 days prior to first study treatment; recovery of treatment-related toxicity consistent with other eligibility criteria   History of exposure to cumulative doses of anthracyclines   History of radiation therapy within 14 days of first study treatment. The participant must have recovered from any resulting acute toxicity (to Grade </=1) prior to first study treatment.   Metastatic central nervous system (CNS) disease only   Brain metastases which are symptomatic   History of a decrease in LVEF to less than (<) 40% or symptomatic congestive heart failure (CHF) with previous trastuzumab treatment   History of symptomatic CHF (New York Heart Association [NYHA] Classes II-IV) or serious cardiac arrhythmia requiring treatment   History of myocardial infarction or unstable angina within 6 months of first study treatment   Current dyspnea at rest due to complications of advanced malignancy or requirement for continuous oxygen therapy   Current severe, uncontrolled systemic disease (clinically significant cardiovascular, pulmonary, or metabolic disease)   Pregnancy or lactation   Currently known active infection with human immunodeficiency virus (HIV), hepatitis B virus, or hepatitis C virus   History of intolerance (such as Grade 3-4 infusion reaction) or hypersensitivity to trastuzumab or murine proteins or any component of the product