FREE-TO-TOTAL PROSTATE-SPECIFIC ANTIGEN (PSA) RATIO IMPROVES THE SPECIFICITY FOR DETECTING PROSTATE-CANCER IN PATIENTS WITH PROSTATISM AND INTERMEDIATE PSA LEVELS

Objective To investigate the clinical significance of the Gee-to-total prostate-specific antigen (PSA) ratio in improving the specificity of PSA measurement for detecting prostate cancer within the diagnostic i ntermediate range (4-10 ng/mL total PSA) in patients referred for the treatment of urinary symptoms, Patients and methods Serum samples were obtained from 333 consecutive patients with obstructive and irritativ e urinary symptoms. Of these men, 114 had total PSA levels of 4-10 ng/ mL; 22 had prostate cancer (group 1) and 71 had benign prostatic hyper plasia (BPH, group 2), Group 3 consisted of 21 patients with BPH and a chronic indwelling catheter, The concentrations of Gee and total PSA (ProStatus(TM), Wallac Oy, Turku, Finland) and PSII complexed to alpha -1-antichymotrypsin were measured and the free-to-total PSA ratio calc ulated. All patients under 70 years of age or with suspicious findings on digital rectal examination or transrectal ultrasonography underwen t ultrasound-guided sextant prostate biopsies, Of the 114 patients, 10 5 (92%) underwent transurethral resection of the prostate and six (5%) radical retropubic prostatectomy. Results Patients in group 1 had sig nificantly lower median Gee PSA concentrations (0.78 ng/mL vs 1.13 ng/ mL, P<0.001) and a lower free-to-total PSA ratio (12.1% vs 19.9%, P<0. 001) than those in group 2, The differences were similar between group 1 and group 3 (median free PSA in group 3, 1.06 ng/mL, P=0.03, and fr ee-to-total PSA ratio 18.7%, P=0.007), There were no significant diffe rences between patients in groups 2 and 3, The free-to-total PSA ratio had a higher specificity than total PSA at all sensitivity levels, e. g. a threshold free-to-total PSA ratio of 0.20 detected 91% of cancers and spared 48% (group 2) or 46% (group 3) from unnecessary biopsies, The area under the receiver operating characteristic curve for group 1 vs group 2 was 0.56 (total PSA) and 0.78 (free-to-total PSA ratio) an d for group 1 vs group 3 was 0.56 (total PSA) and 0.81 (free-to-total PSA ratio), Conclusion In those patients with extensive symptoms from BPH and requiring surgical treatment, the free-to-total PSA ratio impr oves the specificity for detecting prostate cancer in the diagnostic ' grey zone' of 4-10 ng/mL total PSA, This improvement occurred in patie nts with or without a chronic indwelling catheter for urinary retentio n.