Combining the Prostate Cancer Risk Index (PRIX) with the Presence of Secondary Circulating Prostate Cells to Predict the Risk of Biochemical Failure after Radical Prostatectomy for Prostate Cancer

Introduction: The use of pre- and post-surgery variables has been used to create nomograms in order to identifypatients at high risk of treatment failure. The PRIX nomogram is one such device; we compare the PRIX nomogramwith the presence of secondary circulating prostate cells to predict those men who will undergo treatment failure.Methods and Patients: Men who underwent radical prostatectomy for prostate cancer entered the study. The PRIXscore was calculated from the total serum PSA pre-surgery, the biopsy Gleason score and clinical stage. Circulatingprostate cells were detected from venous blood one month after surgery, using differential gel centrifugation and standardimmunocytochemistry with anti-PSA. A test was considered positive when 1 CPC/blood sample was detected. Patientswere followed up for five years and biochemical failure was defined as a serum PSA >0.2ng/ml. Kaplan-Meier andCox proportional models were used to calculate survival curves. Results: 321 men participated, of whom 131 (40.8%)underwent biochemical failure within 5 years. A higher PRIX score was associated with increased failure risk, as wasthe presence of CPCs. The predictive power of CPCs was significantly higher than the PRIX score. Combining thetwo methods, for equal PRIX scores, scores but CPC positive had a worse biochemical failure free survival than menwith high PRIX scores but CPC negative. For men with PRIX scores of ≥4 the use of CPC detection did not aid in theclinical decision making process. For those with PRIX scores of 0 and 1, CPC detection identified men with a high riskof treatment failure. Conclusions: The combined PRIX/CPC score improved the predictive values of men at high riskof biochemical failure. Both are simple systems that could be incorporated in a general hospital. Further multicenterstudies are warranted to confirm these results.