Prostate-specific antigen (PSA) complexed to alpha1-antichymotrypsin improves prostate cancer detection using total PSA in Japanese patients with total PSA levels of 2.0-4.0 ng/mL.

Abstract

To assess the utility of prostate-specific antigen (PSA) complexed to alpha1-antichymotrypsin (PSA-ACT) in prostate cancer screening in Japanese men with a total PSA level of 2.0-4.0 ng/mL, as improving cancer detection in men with these total PSA levels is a challenge for clinical urologists. Total PSA and PSA-ACT were prospectively assessed and prostate biopsy recommended for patients who met either of two thresholds, i.e. a total PSA of > or = 2.0 ng/mL or a PSA-ACT of > or= 1.5 ng/mL. The diagnostic ability of total PSA and PSA-ACT, and free-to-total PSA ratio and prostate volume-adjusted density were evaluated by receiver operating characteristic (ROC) analysis. Of 1003 men enrolled, 547 met the biopsy criteria and a biopsy was taken in 315 (57.6%) patients. The area under the ROC curve for PSA-ACT (0.679) was significantly greater than that for total PSA (0.601, P = 0.04) and equivalent to that for the free-to-total ratio (0.686, P = 0.911) in 116 men, including 27 with cancer with total PSA levels of 2.0-4.0 ng/mL. PSA-ACT was more specific than the free-to-total ratio at a sensitivity of 95% (36% vs 18%, P < 0.05). The best variable for discriminating between cancer and benign disease in men with PSA levels of 2.0-4.0 ng/mL was PSA-ACT density (area under the curve 0.852) which provided 66% specificity at a sensitivity of 90%. PSA-ACT is better than total PSA and equivalent to the free-to-total ratio for detecting prostate cancer in men with PSA levels of 2.0-4.0 ng/mL, and is thus useful for reducing the number of unnecessary biopsies.