Clinical Relevance of Viable Circulating Tumor Cells detected by PSA-EPISPOT prior Trans-rectal Prostate Biopsy

Background: Accurate new tools are advocated to help clinical decisions from screening to follow-up and salvage-treatment of prostate cancer. We report here the clinical relevance of the PSA-EPISPOT assay for circulating tumor cells (CTCs) detection prior to immediate prostate biopsy. Patients and Methods: One hundred and eleven patients selected to undergo prostate biopsy based on conventional triggering markers were recruited between 2002 and 2006. CTCs in the peripheral blood were detected by the fluoroPSA-EPISPOT assay. Peripheral blood was sampled before prostate biopsy. CTC enumeration was performed with an EpCAM-independent enrichment method followed by the fluoroPSAEPISPOT assay that detects only viable PSA-secreting CTCs. Results: Sixty-three patients were negative biopsy and 48 were positive. Median follow-up was 69.5 months [0.8 – 115.8]. Viable CTCs were detected in 12/63 negative biopsy patients (19%) and 23/48 positive biopsy patients (47.9%). CTC mean count was significantly higher in positive biopsy patients (2 ± 3.1) than in negative biopsy patients (0.7 ± 1.9; p=0.0015). PSA-EPISPOT characteristics were respectively 47.92%, 80.95%, 65.71%, 67.11%, 66.67% for sensitivity, specificity, positive and negative predictive value and accuracy. PSAEPISPOT was better than random to predict positive biopsy but not different from total PSA. Its relation to other markers made the PSA-EPISPOT assay not eligible to multivariate logistic regression. Conclusion: This report indicates that PSA-EPISPOT technique was able to detect CTCs in patients screened for prostate cancer. Despite interesting characteristics, it was not sensitive enough to prevent each unnecessary prostate biopsy. Further analyses are mandatory to assess the prognosis value of the PSA-EPISPOT assay in positive biopsy patients.