In this study, 50 women with either HER2+ or triple negative metastatic breast cancer but no known brain metastases will be recruited at the Sunnybrook Odette Cancer Centre. They will be randomized to undergo either routine MRI screening of their brain every 4 months for 1 year or standard-of-care (MRI only if symptoms of brain metastases develop). Patients will complete questionnaires about quality of life and cancer-related anxiety throughout the study. To determine why some cancers spread to the brain and others do not, blood samples will be collected to analyze the genetic makeup of patients' breast cancers. Finally, a novel MRI imaging technique that detects abnormal metabolism in the brain will be used to help detect brain metastases even earlier than the standard MRI.

If results are promising, we will conduct a large multi-centre randomized trial to determine whether screening for brain metastases can help them live longer with improved quality of life.

Please see trial details below.

Inclusion Criteria:

1. Age ≥18

2. Triple negative or HER2+ breast cancer (ASCO/CAP guidelines 2018)*

3. MBC, as defined as distant disease outside of the breast and local/regional lymph nodes. Physicians' clinical judgment will be used to determine the possible need for biopsy in confirming a MBC diagnosis. However, biopsy of a metastatic site is not required for pathologic confirmation of stage IV disease.

4. Diagnosis of metastatic disease within 12 weeks prior to study enrollment.

5. No symptoms of BrM or known asymptomatic BrM at study entry.

6. 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.

   • This will generally be based on the primary cancer but in the event that a metastatic site is biopsied eligibility will be based on the ER, PR and HER2 profile of the metastasis.

Exclusion Criteria:

1. Inability to participate in an MRI screening program as determined by the patient and/or physician. This may be on the basis of severe claustrophobia, performance status that limits additional testing, or a metal foreign body that would prevent MRI imaging.
2. Inability to provide informed consent. Notably participants who require translators are allowed to enroll.
3. Creatinine clearance <30 mL/min using the Cockcroft-Gault equation.
4. Established need for brain imaging apart from the breast cancer diagnosis (e.g surveillance for an aneurysm).
5. ECOG Performance status >2.
6. Pregnancy.
7. Grade 3+ allergy to Gadavist IV contrast (CTEP Adverse Event Reporting System).

IPD which does not include any patient identifiers will be considered but will require Research Ethics Board approval and appropriate legal contracts between collaborating institutions to ensure protection of patient data.

The study documents (protocol, statistical analysis plan and informed consent form) can be made available at any time. Data may be available after study completion.

Research Ethics Board approval and appropriate legal contracts between collaborating institutions will be required prior to data-sharing to ensure protection of patient data.