From Discovery to Diagnosis: A Perspective for Circulating Tumor Cells in Personalized Oncology

Circulating tumor cells (CTCs) are cells shed from tumors into the bloodstream, providing a unique source of information on tumor biology. CTCs can be collected through liquid biopsy, offering a noninvasive option to track cancer progression and treatment responses. Whereas ctDNA gives valuable insights into genomic alterations, CTCs allow for the direct analysis of cellular protein and RNA expression, essential for identifying targetable markers and resistance mechanisms. Resistance to cancer therapies is often due to genetic and phenotypic adaptations within tumor cells. CTC analysis can help track these adaptations, providing real-time insights into evolving resistance mechanisms and suggesting alternative therapies. Enumeration and molecular characterization of CTCs provide unique insights into the biology of cancer metastasis as well as clinically relevant information on tumor evolution, risk assessment, and therapy response in individual patients with solid malignancies.