This joint scientific project, part of the German Cancer Aid's "Translational Oncology" funding program, utilizes liquid biopsies to explore therapy resistance mechanisms and develop adaptive treatment strategies for metastatic breast cancer. Our subproject aims to enhance CTC detection through diagnostic leukapheresis (DLA), processing larger blood volumes to overcome the challenges of low CTC concentration and distribution. By refining DLA protocols and studying CTC density variations, we seek to improve CTC-based diagnostics and inform future therapeutic strategies. The DETECT-CTCHIGH consortium, coordinated by Prof. Dr. Tanja Fehm from the University Hospital Düsseldorf, includes six academic groups across Germany and is funded by the German Cancer Aid. (https://www.krebshilfe.de/forschen/projekte/foerderschwerpunkte/translationale-onkologie)