Recent progress in cancer biology has revealed the fact that molecular profiles of primary and metastatic cancer are not necessarily the same. Furthermore, evidence of intra-tumor heterogeneity has been disclosed repeatedly. In addition to these, acquiring resistances to chemoradiation therapy is far more rapid than typical predictions. Under these circumstances, physicians are realizing that one biopsy is not enough to predict the direction of cancer progression or extension. Repeated biopsy was proposed in this context. For “re-biopsy”, acquiring blood is much easier compared to regular biopsies of acquiring body tissues. Therefore, CTC or Cell-free DNA is one of the hot topics in clinical and molecular diagnostic fields. The term “liquid biopsy” is used to include these two materials. We utilized a CTC isolation device based on microfluidic principles. Procedures for the extraction of DNA from plasma (Cell-free DNA) is also available. Based on this background, we performed a feasibility study of NGS (Next Generation Sequencing) by analyzing materials from advanced gastrointestinal cancer patients. We have successfully acquired NGS results using these liquid biopsies. We have also investigated the possibility of storing CTCs by evaluating procedures after cytospin using H1975 cells with various fixation conditions under a DIC microscope examination. Because of the paucity of the number of isolated CTCs, H1975 cells were used for this purpose. After cytospin, 95% ETOH and then -80 degrees C storage provided the best results. Attempts at not only NGS but also storage in this sequence of studies have opened new fields of liquid biopsy in clinical laboratories.