Yearly prostate specific antigen and digital rectal examination fluctuations in a screened population.

Abstract

Prostate biopsy is often recommended based on increases in prostate specific antigen and/or abnormal digital rectal examination. We investigated the stability of a single positive test during the next 3 consecutive years. A total of 2,578 participants in a San Antonio screening cohort with 2 or more consecutive annual prostate specific antigen and digital rectal examination tests were identified. Occurrences of an increased prostate specific antigen (2.5 ng/ml or greater) followed by 1 or more nonincreased prostate specific antigen results were compared with similar fluctuations of digital rectal examination from abnormal to normal. In 2,272 men who did not have a biopsy during the study, in 23.3% of 744 incidences of an increased prostate specific antigen with 1 year of followup, the next prostate specific antigen was not increased. In 19.5% of 462 incidences of an increased prostate specific antigen with 2 years of followup, the next 2 consecutive prostate specific antigen levels were not increased. Finally, in 17.5% of 285 incidences of an increased prostate specific antigen with 3 years of followup, the next 3 consecutive prostate specific antigens were not increased. Rates were similar but lower in 221 men with 1 or more negative biopsies during the study and in 85 men in whom prostate cancer eventually developed during the study. In contrast, approximately 70% of abnormal digital rectal examinations were normal the following year even in patients with prostate cancer, and in the majority of incidences remained normal the next 2 to 3 consecutive years. Occurrences of reversed prostate specific antigen cut point or abnormal digital rectal examination based decisions to biopsy 1 or more years after the initial test are not uncommon, suggesting repetition of these tests.