Metastatic disease is the most common cause of death in patients with breast cancer. In the metastatic setting, no clear guidelines exist to inform therapeutic decisions, and there is a need for novel technologies to drive personalized treatment choices. Dr. Wilbert Zwart at the Netherlands Cancer Institute (NKI) and his collaborators are developing a 3D-printed cell support matrix that allows short-term culturing of metastatic breast cancer cells. This system has a high culture success rate and maintains a mixture of cancer and non-cancer cells that are present in the patient’s tumor. It also allows for the live culture of a sufficient number of cells for assessing drug response ex vivo within days after they are isolated from the patient. The goal of this project is to determine whether ex vivo treatment response is predictive of treatment response in patients. Toward this goal, the team will use this novel platform for drug intervention studies on breast cancers that have metastasized to the pleural cavity. If shown to be predictive, the platform would provide clinicians with an evidence-based treatment selection approach. In addition, the model would enable research into the basic biology of metastatic cancer in a clinically relevant setting.