Brain Monitoring for High Risk of Brain Metastases in Metastatic Breast Cancer

Inclusion Criteria:

• Patients over 19 years
• Pathologically documented breast cancer that:

1. is unresectable or metastatic ;
2. has confirmed HER2 positive expression according to American Society of ClinicalOncology- College of American Pathologists (ASCO-CAP) guidelines or triplenegative breast cancer

• No prior systemic palliative treatment of metastatic breast cancer
• Must have provided informed consent for study participation before performance of anystudy-specific procedures or tests

Exclusion Criteria:

• History of prior treatments about brain metastases or leptomeningeal metastases
• Symptomatic brain metastases at screening period
• Has received more than second-line systemic treatments (including endocrine therapy)
• For subjects who have difficulty lying down or who have claustrophobia, they canundergo sedation during brain MRI
• History of hypersensitivity reaction to contrast or drug allergic reaction
• Patients who inserted metallic prosthesis (pacemaker, denture, hearing aid, aneurysmclip, metallic material of eyeball, artificial joint, insulin pump, chemo-port,temporary tissue expander for breast reconstruction, etc) can be conducted afterconsultation with investigator before MRI.
• Has known psychiatric or substance abuse disorders that would interfere withcooperation with the requirements of the trial.
• Social, familial, or geographical factors that would interfere with studyparticipation or follow-up