The goal of this multi-centre, prospective study is to assess the frequency of asymptomatic brain metastasis in patients with stage IIb or III Triple Negative or HER2 positive breast cancer. The main questions it aims to answer are:

1. What proportion of patients with stage IIb or III Triple Negative or HER2 positive breast cancer have asymptomatic brain metastases identified on a screening contrast-enhanced magnetic resonance imaging (MRI) of the brain?
2. How do patients feel about undergoing brain imaging to screen for asymptomatic brain metastasis?
3. What clinical as well as liquid and tissue-based biomarkers are associated with asymptomatic detection of brain metastasis?

Participants will undergo brain imaging, provide one blood sample (for analysis of ctDNA), and complete the Testing Morbidities Index (TMI) questionnaire after imaging is done. Procedures may take place either prior to or after completion of (neo)-adjuvant systemic therapy; however, the study interventions must take place within 18 months of initial breast cancer diagnosis.

Inclusion Criteria:

1. Age > 18.
2. Triple Negative OR HER2+ breast cancer (as per 2018 ASCO/CAP guidelines).
3. Stage IIb or III disease.
4. Patients with a prior or concurrent malignancy whose natural history or treatment does not have the potential to interfere with the safety or efficacy assessment of the investigational regimen may participate.
5. Ability to understand and the willingness to sign a written informed consent document.

Exclusion Criteria:

1. Creatinine clearance <30 mL/min using the Cockcroft-Gault equation (in accordance with the product monograph for Gadavist IV contrast.
2. Pregnant women are not permitted to participate given that the safety of IV contrast is unknown in this population.
3. Patients with central nervous system symptoms that are concerning for brain metastases that would otherwise be referred for brain imaging.