This is a prospective study using [68Ga]Ga DOTA-5G PET/CT imaging in patients diagnosed with metastatic/advanced invasive lobular breast cancer (LBC).

This is a phase I investigator-initiated study that will investigate [68Ga]Ga DOTA-5G in patients with metastatic/advanced invasive LBC. 30 patients diagnosed with LBC will be enrolled over a 24-month period.

We hypothesize that a) [68Ga]Ga DOTA-5G will detect lesions in patients with invasive LBC, b) [68Ga]Ga DOTA-5G will be safe and well tolerated, and that c) [68Ga]Ga DOTA-5G PET/CT is more sensitive than 18F-FDG PET/CT at detecting lesions.

Inclusion Criteria:

• (Ability to understand and willingness to sign a written informed consent document.
• Men and women age ≥ 18 yrs
• Confirmed presence of metastatic/advanced invasive lobular breast cancer and measurable disease per RECIST (version 1.1) or PERCIST
• Available archival tumor tissue
• Eastern Cooperative Oncology Group Performance Status ≤ 2
• Hematologic parameters defined as: Absolute neutrophil count (ANC) ≥ 1000 cells/mm3,Platelet count ≥ 100,000/mm3, Hemoglobin ≥ 8 g/dL.
• Blood chemistry levels defined as: AST, ALT, alkaline phosphatase ≤ 5 times upper limit of normal (ULN), Total bilirubin ≤ 2 times ULN, eGFR >60 mL/min/1.73m*2
• Anticipated life expectancy ≥ 3 months
• Able to remain motionless for up to 30-60 minutes per scan.

Exclusion Criteria:

• Pregnant and lactating women
• Prisoners
• Concurrent malignancy of a different histology that could confound imaging interpretation.
• Patients who cannot undergo PET/CT scanning because of weight limits(>350lbs)