THE INFLUENCE OF PROSTATE VOLUME ON THE RATIO OF FREE TO TOTAL PROSTATE-SPECIFIC ANTIGEN IN SERUM OF PATIENTS WITH PROSTATE CARCINOMA AND BENIGN PROSTATE HYPERPLASIA

BACKGROUND. Determining the ratio of free to total prostate specific a ntigen (f-PSA to t-PSA, calculated as the percentage of f-PSA [f-PSA%] ) in serum allows for a clearer distinction between patients with pros tate carcinoma (PCa) and patients with benign prostate hyperplasia (BP H) than determining the level of t-PSA alone. To find influencing fact ors on f-PSA%, the authors investigated prostate volume, TNM classific ation, and tumor stage. METHODS, The authors measured f-PSA and t-PSA in 36 men with untreated PCa (tumor classification: T1, 2, 3pN0, MO), 44 patients with BPH, and 54 healthy controls. Prostate volume was det ermined by transrectal ultrasound. RESULTS, The median values of t-PSA and f-PSA% were 7.8 mu g/L and 10.5% in PCa patients, 4.3 mu g/L and 20.8% in patients with BPH, and 1.4 mu g/L and 23.6% in the control gr oup. Patients with PCa had a significantly lower proportion of f-PSA t han BPH patients and healthy men. There was no correlation of f-PSA% t o TNM stage or tumor grade. In PCa patients a significant positive cor relation (correlation coefficient [r] = 0.51, P < 0.001) was found bet ween f-PSA% and prostate volume, whereas there was no significant corr elation in BPH patients (r = -0.27, P > 0.05). There was a significant difference in f-PSA% between PCa and BPH patients with prostate volum es smaller than 40 cm(3) (9.0% us. 21.6%, P < 0.01) but not between pa tients in these 2 groups with prostate volumes exceeding 40 cm(3) (15. 1% vs. 18.2%, P = 0.11). CONCLUSIONS, Determining the ratio of f-PSA t o t-PSA to discriminate between PCa and BPH patients yields significan t results only in men with a prostate volume of less than 40 cm(3). (C ) 1997 American Cancer Society.