Association between one-time prostate-specific antigen (PSA) test with free/total PSA ratio and prostate cancer mortality: A 30-year prospective cohort study

Abstract

Objectives: To explore if there is a long-term association between baseline prostate-specific antigen (PSA), including free/total PSA ratio and long-term (30-year) risk for prostate cancer death. Subjects and methods: In all, 1782 men were screened for prostate cancer through PSA analysis. Some years later, frozen plasma samples were used to calculate the ratio of free to total PSA (f/t PSA). At 30-year follow-up, baseline PSA and f/t PSA were compared with recent data extracts from the Swedish Cause of Death Registry and Swedish Cancer Registry. PSA values and f/t PSA values were treated as continuous variables in a multivariable analysis and also stratified according to their distribution and useful clinical thresholds. Results: Risk of death from prostate cancer after 30 years of follow-up was significantly increased with a higher baseline PSA level, with the hazard ratio being 1.04 (95% confidence interval 1.03–1.09) per increase of one unit of PSA. Adding f/t PSA increased the model's ability to discriminate (concordance index 0.84–0.88). Men with PSA levels <1.0 ng/mL had a very low long-term risk of prostate cancer death (1.2% risk). An f/t PSA ≥ 0.25 extended the low-risk range to PSA < 2.0 ng/mL (1.5% risk). Conclusion: Prostate-specific antigen testing can be carried out less frequently or can be discontinued in men aged 55–70 years if their PSA levels are <2.0 ng/mL and the f/t PSA is ≥0.25.