The free-to-total serum prostatic specific antigen ratio as a predictor of the pathological features of prostate cancer.

Abstract

To analyse the role of the ratio of serum free (f) to total (t) prostatic specific antigen (f/tPSA) as a predictor of the pathological features in patients with clinical stage T1c disease submitted for radical prostatectomy. Total and fPSA were determined before surgery in 76 consecutive patients with clinical stage T1cN0M0 disease and a serum tPSA level of 4-20 ng/mL. The pathological stage was defined as organ-confined in 47 (62%), with capsular penetration in 27 (35%) and seminal vesicle infiltration in two (3%). In 18 of the specimens (24%) the surgical margins were positive. The pathology was favourable in 41 patients (55%). Total and fPSA were determined using the Tandem and Tandem-free PSA immunoassays (Hybritech Inc, Belgium) The mean tPSA was: 8.7 ng/mL when the tumour was organ-confined and 8.6 ng/mL when the disease was extraprostatic (P>0.05); 8.4 ng/mL when the tumour was specimen-confined and 9.3 ng/mL when positive margins or seminal vesicle involvement were detected (P>0.05); and 8.3 ng/mL when the pathology was favourable and 9.0 ng/mL when unfavourable (P>0.05). The f/tPSA was 11.8% when the tumour was organ-confined and 9.1% when it was not (P<0.03), 11.9% when the tumour was specimen-confined and 7.6% when not (P<0.002) and 12.1% when the pathology was favourable and 9.1% when unfavourable (P<0.008). A threshold of 11% f/tPSA provided an odds ratio for organ-confined disease of 2.7, for specimen-confined disease of 7.6 and for a favourable pathology of 3.9. The f/tPSA seems to provide useful information in the prediction of the pathological features of patients with clinical T1c prostate cancer and a tPSA of 4.1-20 ng/mL.