Extended use of P504S Positive Primary Circulating Prostate Cell Detection to Determine the Need for Initial Prostate Biopsy in a Prostate Cancer Screening Program in Chile

Background: To determine the frequency of primary circulating prostate cells (CPC) detection accordingto age and serum PSA levels in a cohort of men undergoing screening for prostate cancer and to determinethe diagnostic yield in those men complying with the criteria for prostate biopsy. Materials and
Methods: Aprospective study was carried out to analyze all men evaluated in a hospital prostate cancer screening program.Primary CPCs were obtained by differential gel centrifugation and detected using standard immunocytochemistryusing anti-PSA, positive samples undergoing a second process with anti-P504S. A malignant primary CPC wasdefined as PSA+ P504S+, and a test positive if 1 cell/4ml was detected. The frequency of primary CPC detectionwas compared with age and serum PSA levels. Men with a PSA >4.0ng/ml and/or abnormal rectal examinationunderwent 12 core prostate biopsy, and the results were registered as cancer/no-cancer and compared with thepresence/absence of primary CPCs to calculate the diagnostic yield.
Results: A total of 1,117 men participated;there was an association of primary CPC detection with increasing age and increasing serum PSA. Some 559 menunderwent initial prostate biopsy of whom 207/559 (37.0%) were positive for primary CPCs and 183/559 (32.0%)had prostate cancer detected. The diagnostic yield of primary CPCs had a sensitivity of 88.5%, a specificity of88.0%, and positive and negative predictive values of 78.3% and 94.9%, respectively.
Conclusions: The use ofprimary CPCs for testing is recommended, since its high negative predictive value could be used to avoid prostatebiopsy in men with an elevated PSA and/or abnormal DRE. Men positive for primary CPCs should undergoprostate biopsy. It is a test that could be implemented in the routine immunocytochemical laboratory.