Place du -2proPSA et de l'index phi dans la détection précoce du cancer de prostate : évaluation sur une série de 452 patients. [Use of [-2] pro PSA and phi index for early detection of prostate cancer: A prospective of 452 patients]
Résumé
Introduction Early detection of prostate cancer (Pca) is a real challenge to reduce morbidity and mortality while avoiding over-diagnosis and over-treatment. The prostate specific antigen (PSA) is characterized by its imperfections justifying the evaluation of new serum or urinary specific markers allowing a better selection of patients at risk of developing aggressive Pca. Aim To compare the value of -2pro PSA and phi index to total and free PSA. Methods Serum sampled from 452 patients from two university centers were used to determine levels of PSA before performing biopsies. The patients were included in this study based on the PSA serum concentration between 1.6 ng/mL and 8 ng/mL according to the WHO international standard. All biopsies were performed according to a standardized protocol consisting of 12 cores or more. Sera were analyzed centrally in one of the two institutions with on a single analyzer. Sera from 243 prostate cancer and 208 negative biopsies patients have been taken into account. Results Sera were analyzed blinded for total PSA, free PSA and [-2] proPSA using Access® immunoassay method from Beckman Coulter. The Prostate Health Index (phi) was calculated using the formula phi = ([-2] proPSA/fPSA) × sqrt (PSA). The median value of the phi index is significantly (P > 0.0001) higher for patients with cancer (phi = 65.8) compared to patients with negative biopsies (phi = 40.6). At a given sensitivity, the phi index significantly increases the specificity of detection of prostate cancer compared to other markers. Conclusion The phi index currently appears as the best predictor of prostate cancer for patients with a total PSA between 1.6 and 8 ng/mL according to the WHO standard. The improvement in specificity of the phi index over tPSA could reduce significantly the numbers of unnecessary biopsies. Whether this new biomarker could be an indicator of aggressive prostate cancer remains to be confirmed.