Optimal Measure of PSA Kinetics to Identify Prostate Cancer

Abstract

To compare different tools for evaluate prostate-specific antigen (PSA) kinetics before prostate biopsy, such as PSA velocity, PSA slope, natural logarithm PSA slope (lnPSA slope), and PSA doubling time (PSADT). This study was conducted involving 325 male patients evaluated with transrectal ultrasound-guided biopsy of prostate. Patients with at least three consecutive PSA measurements taken in at least 24 months entered in the study. We estimated PSA slope from the slope of the least squares regression line fit to PSA versus time in years; PSA velocity was calculated as the running average of the rate of change during at least three consecutive assays. The acceleration of PSA (lnPSA slope) was calculated as the slope of lnPSA versus time, where ln is the natural logarithm. PSADT was calculated using the formula: PSADT = ln 2/(lnPSA slope). We found a total of 74 cancers at the ultrasound guided prostate biopsies. At the receiver operating characteristic (ROC) analysis, lnPSA slope (area under the curve [AUC], 0.793) evidenced better results than PSA (AUC, 0.585; P <0.001), PSA velocity (AUC, 0.734; P <0.009), PSA slope (AUC, 0.752; P <0.043), and PSADT (AUC, 0.516; P <0.001). The results for PSA, PSA velocity, PSA slope, and lnPSA slope were significantly higher in patients with prostate cancer than in controls. The results of the present study suggest that lnPSA slope may be useful for prostate cancer diagnosis. At the ROC analyses, the lnPSA slope AUC was better than that of PSA, PSA velocity, PSA slope, and PSADT.