Isolated, disseminated and circulating tumour cells in prostate cancer.

The loss of single cells from a tumour cell cluster marks an early event in the metastatic process of cancer progression. Although the metastatic cascade in prostate cancer is yet to be fully understood, monitoring circulating tumour cells (CTCs) and quantifying the load of tumour cell dissemination is currently being implemented into routine clinical practice for diagnosing minimal residual disease (MRD), estimating prognosis and monitoring treatment success. Current methods for enrichment of CTCs or disseminated tumour cells (DTCs) and detection of MRD rely on the expression of specific marker genes or proteins that might be altered during the process of tumour cell dissemination, therefore disrupting tumour cell detection. The tumour origin and malignant potential for metastasis of marker-positive cells is not yet clear. Some studies have demonstrated the potential of CTCs or DTCs as prognostic or predictive markers, leading to the increasing implementation of CTC measurement as an end point in clinical trials.