Circulating tumour cells (CTC) are identified exploiting their protein/gene expression patterns or distinct size compared to blood cells. Data on CTC in bladder cancer (BC) are still scarce. We comparatively analyzed CTC enrichment by AdnaTest ProstateCancerSelect (AT) and ScreenCell®Cyto (SC) kits, combined with identification by EPCAM, MUC1, and ERBB2 expression and by cytological criteria, respectively, in 19 nonmetastatic (M0) and 47 metastatic (M+) BC patients, at baseline (T0) and during treatment (T1). At T0, CTC positivity rates by AT were higher in M+ compared to M0 cases (57.4% versus 25%, p = 0.041). EPCAM was detected in 75% of CTC-positive samples by AT, showing increasing expression levels from T0 to T1 (median (interquartile range, IQR): 0.18 (0.07-0.42) versus 0.84 (0.33-1.84), p = 0.005) in M+ cases. Overall, CTC positivity by SC was around 80% regardless of clinical setting and time point of analysis, except for a lower occurrence at T1 in M0 cases. At T0, circulating tumour microemboli were more frequently (25% versus 8%) detected and more numerous in M+ compared to M0 patients. The approach used for CTC detection impacts the outcome of CTC studies. Further investigations are required to clarify the clinical validity of AT and SC in specific BC clinical contexts.
