Ratio of free-to-total prostate specific antigen correlates with tumor volume in patients with increased prostate specific antigen

Purpose: We evaluated the relationship between the ratio of free-to-total prostate specific antigen (PSA) and prostate pathology, including grade, stage and tumor volume, among patients with prostate cancer who underwent radical prostatectomy. Materials and Methods: We prospectively analyzed 54 consecutive patients with prostate cancer who underwent radical prostatectomy and in whom frozen serum was available for assessment of free-to-total PSA ratio. Pathological review was done with whole mount sections, and total tumor volume was determined by planimetry. Comparison between free-to-total PSA ratio and pathological parameters was performed using the Pearson correlation coefficient. Results: Among the 54 patients mean total and free-to-total PSA ratio were 5.81 and 14.2 ng./ml., respectively, and free-to-total PSA ratio directly correlated with prostate volume (p = 0.037), and inversely correlated with Gleason score (p = 0.012) and extracapsular disease (p = 0.0074). Furthermore, there was a significant relationship between free-to-total PSA ratio and pathological stage pT2a/b in 39 cases versus pT3a/b in 15 (p = 0.005). Overall, there was no correlation between free-to-total PSA ratio and tumor volume. However, among 37 patients with an increased PSA, defined as greater than 4.0 ng./ml., a significant inverse relationship between free-to-total PSA ratio and tumor volume was identified (p = 0.01). Among this subset there was only a weak correlation with prostate volume (p = 0.049). Conclusions: Our findings suggest that free-to-total PSA ratio may be predictive of tumor biology among those patients with a total PSA of greater than 4 ng./ml. as evidenced by good correlation with tumor grade and volume. This finding appears to be independent of prostate volume. These preliminary results suggest the need for additional studies among patients with an increased PSA designed to evaluate the potential role of free-to-total PSA ratio in combination with traditional clinical variables in the prediction of prostate cancer pathology.