Pilot study evaluating antibody imaging to predict response to antibody-drug conjugate (ADC) therapy.

Prior treatment

• Patients already treated with Trastuzumab deruxtecan (T-DXd)

Other illness

• Hypersensitivity at the ImmunoPET radioligands injection

Other

• Male patients
• Patients who are claustrophobic or unable to remain still for 30 minutes
• Female participant who is pregnant, breastfeeding, or planning to become pregnant while enrolled in this study or within 90 days after the final administration of study treatment
• Person deprived of their liberty or under protective custody or guardianship.

• Female patient must have signed a written informed consent prior to any trial specific procedures. When the patient is physically unable to give their written consent, a trusted person of their choice, independent from the investigator or the sponsor, can confirm in writing the patient’s consent;
• Patients enrolled in the prospective cohort of the OASIS study (NCT07259226);
• Patient with locally advanced or metastatic breast cancer eligible to receive T-DXd as part of their standard care;
• At baseline imaging at least two “target” lesions fulfilling the following criteria: (1) anatomically transaxial diameter ≥ 1.5 cm and measurable per RECIST1.1. and (2) metabolically assessable with a maximum standard uptake value corrected for lean body mass (SUVmax) ≥ 1.5 x SUVmean + 2 standard deviations (SD) of the liver measured in a 3-cm-diameter spherical volume of interest (VOI) in normal liver parenchyma;
• Patients must be willing and able to comply with the protocol for the duration of the trial;