Relationship between prostate size and percent free prostate-specific antigen in patients with operable prostate cancer

Background: The free-to-total prostate-specific antigen ratio is the best m arker for optimizing prostate cancer detection. The main problem with studi es of percent free PSA is the variability of reported cutoff values. Objectives: To evaluate the influence of prostate size on the ratio of free to total PSA. Methods: The study group included 58 patients (mean age 66.4 years) with cl inically localized prostate cancer treated surgically at our institution. T otal PSA and free PSA levels were measured by a solid phase enzyme immunoas say test (Hoffman-La Roche, Basel, Switzerland). The percent free PSA was c ompared with prostate size as determined from the surgical specimen. Results: A direct relation was noted between prostate size and the percent free PSA value (r=0.49, P=0.0001). Mean percentage free PSA was 9%+/-0.004 in men with normal-sized gland while in men with large prostate (>60 g) the average percent free PSA was 15.9+/-0.09 (P=0.001). Conclusions: In patients with prostate cancer the percent free PSA level is influenced by the gland size. The larger the prostate the higher the propo rtion of the free PSA. Such information may have influence on the recommend ation for prostate biopsy in screening programs for early detection of pros tate cancer.