Circulating tumour cells as biomarkers of prostate, bladder, and kidney cancer.

Circulating tumour cells (CTCs) have been studied as biomarkers of a number of solid malignancies. Potential clinical applications for CTC analysis include early cancer detection, disease staging, monitoring for recurrence, prognostication, and to aid in the selection of therapy. In the field of urologic oncology, CTCs have been most widely studied as prognostic biomarkers of castration-resistant prostate cancer. Additionally, emerging data support a role for CTCs to help identify which patients are most likely to respond to novel androgen-pathway targeted therapies, such as abiraterone and enzalutamide. CTCs have also been studied as predictive biomarkers of bladder cancer, in particular as a means to identify patients whose disease has been clinically understaged. Less is known regarding CTCs in kidney cancer; this has been attributed to the fact that a minority of renal tumours express EpCAM, the epithelial cell surface protein commonly used by CTC assays for positive cell selection. However, alternative approaches using markers specific for kidney cancer are being explored.