HER2-PET: Predicting T-DXd Efficacy and HER2 Heterogeneity

The study will be conducted as an open-label, single-center, Phase II clinical study, with a planned enrollment of 70 patients with locally advanced or metastatic HER2-positive and HER2-low breast cancer who are intended to receive at least two cycles of T-DXd monotherapy. All patients receiving T-DXd treatment must meet current clinical indications. After screening and enrollment, participants will undergo FDG-PET scans and free-of-charge HER2-PET scans prior to T-DXd treatment, with tissue biopsies performed as needed. Participants will receive single-agent T-DXd treatment until disease progression, with additional tissue biopsies performed as needed.This study will integrate and analyze patients' baseline clinical characteristics, treatment efficacy, and prognostic information, along with HER2 expression levels and HER2 expression heterogeneity as assessed by HER2-PET, to evaluate the feasibility of guiding T-DXd treatment in patients with advanced breast cancer.