[18F]FTT Positron Emission Tomography for the Measurement of PARP Tumor Expression in Patients With Metastatic Breast Cancer

Inclusion Criteria: * Patients must have histologically confirmed invasive breast cancer with metastatic disease * Patients must be candidates for treatment with PARP inhibitor as a single agent or for PARP inhibitor in combination with an ICI per treating physician discretion * Patients must have evaluable disease or at least one measurable lesion that can be assessed at baseline by CT (or magnetic resonance imaging \[MRI\]) per Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 * Age \>= 18 years * Karnofsky performance status (KPS) \>= 50% or Eastern Cooperative Oncology Group (ECOG) performance status 0-2 * Archival tissue (formalin-fixed paraffin-embedded \[FFPE\]) from at least one metastatic site biopsy should be available prior to study enrollment; if archival tissue is not available, then a metastatic site biopsy will be required during the study screening period * Patient must be willing to proceed with an on-treatment biopsy of metastatic site if an on-treatment \[18F\]FTT PET will be performed (at 12 ± 4 weeks after starting PARP inhibitor ± ICI treatment) * For women of childbearing potential, a negative serum pregnancy test is required within 7 days prior to \[18F\]FTT PET imaging on day 1. For women who obtain on-treatment (12-week) \[18F\]FTT imaging, a negative serum pregnancy test will be required within 7 days prior to \[18F\]FTT PET imaging * Men and women of reproductive potential need to agree to employ two highly effective and acceptable forms of contraception throughout their participation in the study * Patient is willing and able to comply with the protocol for the duration of the study including undergoing treatment and scheduled visits and examinations * Ability to understand and the willingness to sign a written informed consent document. Informed consent must be provided prior to any study specific procedures Exclusion Criteria: * Patients with prior myelodysplastic syndrome or acute myeloid leukemia due to rare risk associated with PARP inhibitor therapy * Pregnant or breastfeeding women * Patient with a known hypersensitivity to the proposed PARP inhibitor product * Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements * Patients unable to swallow orally administered medication and patients with gastrointestinal disorders likely to interfere with absorption of PARP inhibitor therapy (per investigator's discretion)