Circulating tumour cells (CTCs) are unique cells that originate from the main tumor site. They circulate in the bloodstream, and are implicated in metastasis, immune evasion and recurrence in various cancers. Associated biomarkers of importance for CTC detection include epithelial cell adhesion molecule (EpCAM), human epidermal growth factor receptor 2 (HER2), programmed death ligand-1 (PD-L1), cluster of differentiation 45 (CD45) and other cancer-specific biomolecules. Their roles as standalone biomarkers, have been thoroughly examined in CTC detection, isolation and targeting.

This review collates key findings on CTC characteristics and biomarker identification. The most recent CTC isolation and detection technologies are discussed, along with individual approaches based on inclusion and exclusion of cell-specific biomarkers. Emerging treatments integrating CTCs, including nanocarrier-mediated drug delivery, have been analyzed. We have discussed both the physical and research barriers in the current landscape.

Recent advances have determined that such biomarkers are more reliable when associated with secondary biomarkers, due to concerns regarding immune evasion and low sensitivity. The identification of these molecules has fast-tracked the development of several groundbreaking technologies.

The prognostic and predictive role of CTCs in various cancers revealed promising results. The development of integrative therapeutics can enhance patient survival and quality of life. These advancements depend on addressing key issues, such as molecular characterization and low abundance of CTCs.