Lund University researchers report that precision-cut bladder tumor slices preserve immune cells and functional activity for up to six days, enabling ex vivo drug testing. The results showed response patterns to the checkpoint inhibitor nivolumab that mirrored clinical response rates. The ex vivo “living test bed” approach aims to bridge the gap between in vitro assays and patient-level outcomes by maintaining tumor architecture and microenvironment features. For platform developers, this offers a pathway to evaluate drug response faster than traditional trial timelines. If further validated, such tissue-slice systems could become decision-support tools for optimizing immunotherapy strategies by testing candidates directly on patient tumor material.