Positron emission tomografy with [68Ga]Ga-ABY-025

This is a prospective, multi-center, open-label, exploratory diagnostic phase II imaging trial for patients with metastatic breast cancer with at least one line of systemic therapy. The overarching aim of the HER2-Ex PET trial is to study the role of precision imaging utilizing positron emission tomography (PET) with the HER2-specific tracer \[68Ga\]Ga-ABY-025 (hereafter referred to as HER2-PET) in enhancing treatment planning for patients with metastatic HER2-expressing breast cancer Patients will be allocated based on HER2-status on PET and biopsy. Patients with HER2-expressing lesions in a fresh or archived tumour biopsy will be treated with T-DXd. The study hypothesis is that PET/CT precision imaging with a contemporary HER2-radiotracer (\[68Ga\]Ga-ABY-025) can be used and can lead to a potentially better identification of patients who benefit from T-DXd treatment, thereby achieving improved treatment responses as well as fewer side effects. This study's diagnostic approach provides a more individualized treatment strategy. Additionally, this study can potentially give us a better biological understanding of HER2-expressing mBC.