Pulsed Electric Field Ablation for Metastatic Breast Cancer

Inclusion Criteria: 1. Participants must have histologically or cytologically confirmed metastatic breast cancer. 2. Confirmed documented soft tissue involvement via imaging or biopsy, with at least one measurable lesion with a cutaneous and/or subcutaneous component that is at least 1 cm in size but no greater than 5 cm in size and that can be safely accessed under image guidance. Up to 3 lesions that meet these criteria may be treated with PEF ablation therapy. 3. There are no limits on the amount of prior or concurrent anti-cancer therapies, but patients must be medically able (in the opinion of referring provider and treating investigator) to withhold their systemic therapy for breast cancer one week before the PEF ablation and for 2 weeks after the procedure. 4. Age ≥18 years 5. Eastern Cooperative Oncology Group (ECOG) performance status ≤ 2. 6. Adequate Bone Marrow Function: 1. Absolute neutrophil count ≥1,500/microliter (mcL). 2. Platelets ≥100,000/mcL. 7. Not on or able to withhold anticoagulation or antiplatelet therapy per Society of Interventional Radiology periprocedural guideline. 8. Human immunodeficiency virus (HIV)-infected individuals on effective anti-retroviral therapy with undetectable viral load within 6 months (as documented in the medical record) are eligible for this trial. 9. For participants with evidence of chronic hepatitis B virus (HBV) infection, the HBV viral load must be undetectable on suppressive therapy (as documented in the medical record), if indicated. 10. Individuals with a history of hepatitis C virus (HCV) infection must have been treated and cured. For individuals with HCV infection who are currently on treatment, they are eligible if they have an undetectable HCV viral load (as documented in the medical record). 11. Individuals 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 are eligible for this trial. 12. The effects of pulsed electric field on the developing human fetus are unknown. For this reason individuals of reproductive potential must agree to use adequate contraception: (e.g., hormonal or barrier method of birth control; abstinence, etc.) for the duration of study participation and for 4 weeks after last administration of study treatment. Should a study participant become pregnant or suspect pregnancy while participating in this study, they should inform their treating physician immediately. Exclusion Criteria: 1. Has not recovered from adverse events due to prior/concurrent systemic anti-cancer therapy to ≤ Grade 2 (CTCAE v5.0) or baseline (other than alopecia). 2. Individuals with pacemakers or other electronic implant devices. 3. Individuals who are unable or unwilling, or with medical contraindication, to undergo moderate sedation and local anesthesia. 4. Pregnant individuals are excluded from this study because there is unknown risk of PEF on fetus. 5. Breastfeeding/chestfeeding individuals are excluded from this study because there is unknown risk on nursing infants; breastfeeding/chestfeeding should be discontinued prior to initiating study treatment. 6. Individuals with any condition or social circumstance that, in the opinion of the treating investigator, would impair the participant's ability to comply with study procedures.