Development of Patient Derived Xenografts (PDX) in Patients With Breast Cancer

Inclusion Criteria:

• Age ≥18 years.
• Diagnosis of invasive breast cancer treated with neoadjuvant systemic therapy.
• Surgically resectable disease following neoadjuvant systemic treatment.
• At least one of the following must be true:

1. Received at least 2 weeks of neoadjuvant endocrine therapy
2. Received at least 2 months of neoadjuvant chemotherapy with suggestion ofresidual disease on imaging
3. Began neoadjuvant chemotherapy or endocrine therapy but discontinued due toevidence of progressive disease by MRI, ultrasound, or physical examination

• Provide written informed consent.
• Willing to return to enrolling institution for breast cancer surgery.
• Willingness to provide mandatory blood specimens for future research on breast cancerat Mayo Clinic.
• Willingness to provide mandatory tissue specimens for future research on breast cancerat Mayo Clinic.
• Willingness to provide mandatory tissue specimens for the generation of PDX andorganoids to be used future research on breast cancer at Mayo Clinic.

Exclusion Criteria:

• Ineligible for surgery.
• History of prior malignancy <3 years prior to registration. Exceptions fornon-melanoma skin cancer, papillary thyroid cancer, non-invasive cancer (e.g.,carcinoma in situ of the cervix).