A Study of Surgery and Radiotherapy in People With Breast Cancer

Inclusion Criteria:

* Age ≥ 18 years.
* Pathologically-confirmed metastatic breast cancer.
* Oligometastatic breast cancer (≤5 discrete metastatic lesions) without CNS involvement; as seen on standard imaging during initial workup and monitoring prior to registration.
* HER2-positive breast cancer per CAP/ASCO guidelines as determined by staff pathologist (any estrogen or progesterone receptor status).
* Based on size and location, all metastatic sites can be safely treated with either SBRT or resection.
* Enrolled at least 3 months (and up to 12 months) after initiation of first-line systemic therapy AND without evidence of progression as determined by treating clinician (whether clinically or radiographically) during this window. (ie. in the judgement of the treating clinician, based on standard evaluations, all known disease must be controlled prior to enrollment).
* ECOG performance status 0-2; KPS 60-100

Exclusion Criteria:

* Any foci of disease progression during initial 3-12 months of first-line systemic therapy (as determined by treating clinician)
* Escalation of systemic therapy line due to progressive disease (i.e. initiated second-line therapy prior to enrollment).
* Comorbidities precluding receipt of radiotherapy, surgery or standard systemic therapy.
* Intracranial or intrathecal/intramedullary spinal disease (ie. CNS involvement is excluded from the study; epidural/vertebral disease is permitted)
* Prior cancer history requiring chemotherapy within the past 10 years (ie. prior cancers are permitted provided no chemotherapy was administered).

Inclusion of Underrepresented Populations

* Individuals of all races and ethnic groups are eligible for this trial. There is no bias towards age or race in the clinical trial outlined. This trial is open to the accrual of men and women.