The investigators propose to use clinically validated patient avatar technology ("PDXovo") that can test multiple drugs against patients' cancers to identify the most promising systemic therapy for each individual.

The primary goal of this feasibility study is to determine the percentage of patients for whom PDXs are successfully generated within 7-10 days. This will give the investigators an indication of the success rate for providing patients with actionable information if this PDX technology were to be implemented in the clinic. Since the PDXs will also receive the same drug as the patient, there is an opportunity to assess the agreement between the clinical response and the PDX response.

As a secondary goal, the response of PDXs will be compared to the patient's response to systemic therapy, as measured using the objective response rate at 12 weeks +/- 4 weeks (ORR, measured using RECIST 1.1 criteria).

Inclusion Criteria:

1. Age 18+.
2. Metastatic breast cancer irrespective of subtype.
3. Measurable disease as per RECIST 1.1 criteria.
4. Metastatic disease involving the lymph nodes and/or visceral organs is required.
5. Willingness to undergo a biopsy prior to the start of planned systemic therapy.

Exclusion Criteria:

1. Lack of feasibility to obtain a core biopsy of a metastatic site other than the bone (e.g. a metastatic lesion cannot be safely sampled due to proximity to vasculature).
2. Inability to provide informed consent.

Patients with metastatic breast cancer irrespective of subtype prior to receiving either front-line or subsequent line systemic therapy