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 identify patients at high risk of treatment failure. The PRIX nomogram is one such device; we compare the PRIX nomogram with 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 PRIX score was calculated from the total serum PSA pre-surgery, the biopsy Gleason score and clinical stage. Circulating prostate cells were detected from venous blood one month after surgery, using differential gel centrifugation and standard immunocytochemistry with anti-PSA. A test was considered positive when 1 CPC/blood sample was detected. Patients were followed up for five years and biochemical failure was defined as a serum PSA >0.2ng/ml. Kaplan-Meier and Cox 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 was the presence of CPCs. The predictive power of CPCs was significantly higher than the PRIX score. Combining the two methods, for equal PRIX scores, scores but CPC positive had a worse biochemical failure free survival than men with high PRIX scores but CPC negative. For men with PRIX scores of ≥4 the use of CPC detection did not aid in the clinical decision making process. For those with PRIX scores of 0 and 1, CPC detection identified men with a high risk of treatment failure. CONCLUSIONS: The combined PRIX/CPC score improved the predictive values of men at high risk of biochemical failure. Both are simple systems that could be incorporated in a general hospital. Further multicenter studies are warranted to confirm these results.