Abstract This study reports the establishment and pharmacogenomics analyses of tumor heterogeneity in a living biobank of tumor organoids of 213 liver metastases from 102 patients with metastatic colorectal cancer. Successful organoid culturing reflected poorer chemosensitivity and patient survival. Molecular fidelity was demonstrated in tumor-organoid sample pairs, and multi-modal phenotypes were proposed based on organoid morphologies. Cystic morphology was associated with intestinal stem cell markers and higher drug sensitivities, and solid morphology with markers of cancer cell plasticity and aggressiveness. Potential to identify treatments with less vulnerability to tumor heterogeneity was supported by multi-lesion analyses in 65 patients. Complexity of clinical translation was illustrated by two prospective cases of pharmacogenomics-guided treatment, including successful chemotherapy rechallenge and targeted therapy resistance in cancers with low and high tumor heterogeneity, respectively. All pharmacogenomics data are available as a functional oncology resource and serve as reference for an ongoing intervention trial, supporting the interpretation of ex vivo drug sensitivities into prospective clinical “actionability”.