Analysis of PSA velocity in 1666 healthy subjects undergoing total PSA determination at two consecutive screening rounds

Abstract

The study purpose was to assess PSA velocity (PSAV) in healthy subjects in order to establish a reliable cutoff for the differential diagnosis of prostate cancer in a screening setting. We studied a series of 1666 healthy men aged 55 to 74 years undergoing two total PSA determinations at a four-year interval within a population-based randomized screening trial at the Centro per lo Studio e la Prevenzione Oncologica of Florence. First and second screening round PSA assays (PSA1 and PSA2) were carried out with the same method and by the same laboratory. PSAV (PSA1-PSA2/year) was determined in non-cancer subjects in the overall series or in specific age and PSA subgroups, and in subjects with cancer detected at the second screening round. Average PSAV in 1648 non-cancer subjects was 0.07 ng/mL/year (range -2.18+5.99, 95% CI 0.05-0.09); at least one third of subjects showed a decrease in PSA (negative PSAV), mostly of limited magnitude and in the low PSA range. Average PSAV in the 18 cancer patients was 1.16 ng/mL/year (range 0.10-5.6, 95% CI 0.56-1.77), which is significantly higher (p<0.01) than in non-cancer subjects. None of the cancer patients showed a PSA decrease over time. Whatever cutoff was taken for PSAV, its power to discriminate cancer was limited: in particular the previously used PSAV cutoff of 0.75 ng/mL/year would have included only 42 of the 1648 non-cancer subjects (specificity 97.5%) but excluded eight of the 18 cancer patients (sensitivity 55.5%). At best, with the adopted screening protocol PSAV (cutoff 0.10 ng/mL/year) could have spared 27.9% of non-cancer subjects with PSA > or =2.5 ng/mL further diagnostic assessment and 22.7% of non-cancer subjects with PSA > or =4 ng/mL random sextant biopsy, while missing no cancers. This study provides a reliable estimate of PSAV based on a large unbiased population sample. PSAV is widely variable over time, particularly at low PSA values. PSAV might be of value as an indicator for diagnostic assessment and random sextant biopsy in a screening setting.