This is a descriptive, prospective, single centre study. This study will assess PSMA expression via the uptake of radiolabelled PSMA-ligand using PET/CT imaging in mTNBC lesions pre-identified on 18F-FDG PET/CT in order to evaluate the feasibility of molecular radionuclide therapy in refractory mTNBC using the Lutetium-177 radiolabelled PSMA.

Inclusion Criteria:

• Written informed consent in accordance with institutional guidelines and obtained prior to any study procedure
• Women with ≥ 18 years-old
• Eastern Cooperative Oncology Group Performance Status of 0 to 2
• Confirmed diagnosis of progressive metastatic TNBC and presenting measurable disease on 18F-FDG PET/CT (performed within 2 weeks) or Brain MRI in case of progressive brain metastases (performed within 4 weeks) prior to PSMA PET/CT.
• Radiolabelled PSMA PET/CT has to be performed before the next treatment line initiation

Exclusion Criteria:

• Pregnant or lactating patients
• Other active neoplastic disease
• Treatment by another molecule that is the object of investigation within 30 days
• Skin only metastatic disease
• Patients with a significant medical, neuro-psychiatric, or surgical condition, which, in the investigator's opinion, may interfere with completion of the study

Women with ≥ 18 years-old