Prognostic and predictive role of circulating tumor cells

Circulating tumor cells (CTCs) are released from solid tumors in peripheral blood and represent a key mediator of the metastatic process. Several techniques have been developed to isolate and analyze CTCs, though the CellSearch System still represents the only platform to be approved for use in clinical practice. Isolation and enumeration of CTCs have been proven to be significantly associated with prognosis and prediction of response to systemic therapy in several solid tumors, primarily breast, colon-rectal, and prostate cancer. In addition, the isolation of viable CTCs allows to perform extensive molecular phenotyping of these cells, with the possibility to identify new mechanisms of tumor progression and treatment resistance. Moreover, identifying in real-time the evolving molecular portraits of tumors may allow to develop personalized treatment strategies, in line with the new paradigms of precision medicine. Several trials testing the “liquid biopsy” approach are ongoing and results are eagerly awaited.