This chapter focuses on a deep description of the epidermal growth factor receptor (EGFR) expression in circulating tumor cells (CTCs) and its main role in cancer progression, genetic changes related to metastasis , and resistance to treatment. The aberrant behavior of cancer cells is caused by genetic mutations and altered patterns of gene expression. These changes can be responsible for an increase in cell motility but also an ability of CTCs to survival in different microenvironments, as well as developing therapy-resistant clones. Finally, CTCs can acquire the ability to invade distant organs, where metastatic foci can develop.
Keywords: Circulating tumor cells (CTCs); Dormancy; Epidermal growth factor receptor (EGFR); Epithelial mesenchymal transition (EMT); Invasion; Migration; Mutations; Resistant clones.