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

OBJECTIVES: 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. PATIENTS AND METHODS: 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) RESULTS: 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. CONCLUSION: 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.