Circulating Tumor Cells (CTCs) initiated an entire field known as “liquid biopsy”: using a liquid sample, usually blood, that can be obtained easily, serially, and much less invasively than tissue biopsy in cancer throughout a patient’s course of disease to determine prognosis, recurrence, and aid in treatment selection in real-time. More recently, investigators are also analyzing other cancer-related cells circulating in cancer patient blood, such as circulating endothelial cells, circulating immune cells, tumor-educated platelets, as well as other tumor components found in blood such as microRNA, ctDNA, and extracellular vesicles. The 2018 GRC meeting on liquid biopsy will highlight the latest technological breakthroughs while also focusing on the use of these elements to better study the biology of the metastatic process and applications in early diagnosis, cancer monitoring and diagnosis of recurrent disease. Finally, this GRC will provide a forum for researchers young and seasoned to present cutting-edge work and foster interdisciplinary collaboration.