Cancer has been a significant cause of human death in the recent two decades, although detection, diagnosis, and cancer treatments improved and evolved rapidly. Till now, the reasons why some cancer recurs and others do not remain unclear. Since 2004, circulating tumor cell (CTC) has been well-recognized that CTCs in the circulatory system are associated with cancer metastasis. The fundamental studies of CTCs hold tremendous potentials for probing the biological insights on the molecular mechanisms underlying cancer metastasis, cancer-related gene mutation, or biomarker discovery. However, the low purity (one of the natural limitations) of isolated samples often hampered CTC-directed studies' utility. For that, investigators used a well-established device (ODEP, optically-induced-dielectrophoresis) to isolate viable and high-purity CTCs for the following investigations. Investigators team developed a protocol in the past months and succeeded in cultivating CTCs (near 100%) for further drug tests and had a technology platform of organoid culture system developing in 2020. The preliminary results of the experiments showed a promising combination. That urges investigators to propose a 3-year project investigating CTC culture in the organoid system to look at (1) the behavior of CTCs in organ cell background (organoid), (2) the influences of different background cells, (3) the different in-vitro (or in-organoid) response of CTCs to specific drugs (pembrolizumab, nivolumab, cetuximab, cisplatin, 5-FU, taxanes) of head and neck squamous cell carcinoma. In the meantime, investigators will look at the genomic alterations of those CTCs growing fast and well in the organoid systems to find possible precipitating metastasis genes at a scale of cell (CTC) level. Investigators believe that the project is doable and possibly help human cancer control and understanding.