Generation and applications of patient-derived tumor organoid (PDTO) from kidney or prostate cancer tissues. Kidney or prostate cancer tissues of patients are isolated, mechanically minced and then enzymatically digested. The dissociated cell suspension is strained to remove clumpy tissues, washed and embedded within matrigel to form organoids. To compare the diversity and similarity between in vivo tissues and organoids or to analyze a distinct inter-/intratumoral-heterogeneity at the genomic level, genomic/or transcriptomic analysis assessed a degree of variance or similarity of organoids corresponding parental tissues from cancer patients. Genome editing by using CRISPR Cas9 is employed in organoids. Prostate cancer or kidney cancer organoids can be used for preclinical models, such as anti-cancer drug screening, or biobanks.