Sensitivity of a novel immunofluorescent staining method for Circulating tumor cells identification and its clinical application in predicting cancer recurrence in breast cancer

Circulating tumor cells (CTC) enumeration has been clinically adopted as important prognostic factor in different cancers, but many of CTCs isolation or identification apporches did not have clinical data. In this study, we developed a novel indirect immunofluorescent staining method targeting EpCAM or cytokeratin for CTC identification. Peripheral blood samples from twenty healthy donors and thirty-six cancer patients were used for cutoff establishment and sensitivity test. An immunofluorescent intensity threshold value of 5080 for the EpCAM or cytokeratin staining led to highly accurate cell classification (95% sensitivity and >99% specificity), and with the cut-off point of 2 CTCs, the sensitivity of CTC detection was 54.2% (19/35) in the diagnosis of patients with different cancer. Besides, the presence of CTCs defined as having >2 CTCs/7.5 mL might be associated with cancer staging and occurred three weeks earlier than cancer relapse in a breast cancer patient, and thus was consider a clinically useful tool to monitor tumor recurrence during chemotherapy.