Serial prostate specific antigen, free-to-total prostate specific antigen ratio and complexed prostate specific antigen for the diagnosis of prostatecancer

Purpose: The free-to-total prostate specific antigen (PSA) ratio and comple xed PSA have been introduced as adjuncts to total PSA for prostate cancer s creening. Little data exist on the use of these tests for serial PSA screen ing. We compared serial total PSA, the free-to-total PSA ratio and calculat ed complexed PSA in men diagnosed with prostate cancer and matched controls in a population based study. Materials and Methods: We identified 90 men diagnosed with prostate cancer between 1988 and 1996 with at least 3 serial serum samples obtained at 2-ye ar intervals who were participants in the P-Carotene and Retinol Efficacy T rial for the prevention of lung cancer. Samples were available up to 10 yea rs before diagnosis. A total of 90 age matched men from the same cohort wit hout prostate carcinoma were identified as controls. Free and total PSA was measured by the Abbott AxSYM dagger system. Results: Baseline demographics of cases and controls were similar. At basel ine and diagnosis the men with prostate cancer had higher total and complex ed PSA, and a lower free-to-total PSA ratio than controls. Mean followup wa s 5.2 years in cases and 5.5 in controls. The yearly change in PSA paramete rs in cases versus controls was 20.7% versus 3.5% for total, -3.4% versus 0 .2% for free-to-total and 21.5% versus 3.4% for complexed PSA (p <0.0001). At diagnosis PSA alone was estimated to perform with more than 90% specific ity in our model. Conclusions: In this population based study total PSA was superior to the f ree-to-total PSA ratio for predicting the development of prostate cancer. W hile serial changes in free-to-total PSA ratios with time were statisticall y significantly different in men diagnosed with prostate cancer and control s, the magnitude of these serial changes were slight enough to render them clinically insignificant.