Dynamic changes of live/apoptotic circulating tumour cells as predictive marker of response to Sunitinib in metastatic renal cancer

Background: Recently, we developed an apoptotic assay for expanding the monitoring capabilities of the circulating tumour cells (CTC) test during therapy. An automated platform for computing CTCs was integrated with a mAb (M30) targeting a neoepitope disclosed by caspase cleavage at cytokeratin 18 in early apoptosis; we showed that live CTCs were associated with progression, consistent with enhanced cell migration and invasion. The test was first applied here to mRCC. Methods: Live/apoptotic CTCs changes were measured in mRCC patients receiving first-line Sunitinib and compared with circulating endothelial cell (CEC) levels. Results: The presence of EpCAM-positive, live CTCs predicts progression in individual mRCC patient, being associated with distant metastasis under first-line Sunitinib. Synchronous detection of CTCs and CEC levels discloses for the first time an association between their dynamic changes and outcome: a rapid increase of the CEC number as early as the first cycle of therapy is associated with CTC decrease in non-progressed patients, whereas a delayed response of CECs is related to higher CTC values in the progressed group indicating treatment failure. Conclusion: We demonstrated that a delayed response to antiangiogenic treatment indicated by persistent detection of CECs correlates with persistent live CTCs and more aggressive disease.