Objective: To determine whether the proportion of total serum prostate-specific antigen (tPSA) which is unbound or free (free PSA) offers a better discriminant for the detection of patients with prostate cancer (CaP) and those with benign prostatic hyperplasia (BPH) than does serum tPSA alone.
Patients and methods: In a retrospective analysis, the proportion of free PSA was determined in the sera of 60 patients with histologically confirmed localized (n = 39; pT1-3NoMo) and metastatic (n = 21; T2-4NxM+) CaP and 45 patients with BPH. Forty patients with urolithiasis served as a control group. Serum levels of free and total PSA were determined using a chemiluminescent enzyme immunoassay.
Results: Patients with CaP had a lower percentage of free PSA (localized CaP median 8.8%; metastatic CaP median 7.1%) than patients with BPH (median 19.5%) and those with urolithiasis (median 18.8%: P < 0.001). The percentage of free PSA did not differ significantly between patients with clinically localized and metastatic disease.
Conclusion: The determination of the proportion of free PSA enhanced the discrimination between BPH and CaP and may reduce the number of unnecessary biopsies in patients with an elevated PSA. The results warrant further investigations in a broader population to improve the clinical use of serum PSA as a tumour marker for discriminating patients with an early, potentially curable CaP from men with BPH.