PSA Doubling Time as a Predictor of the Outcome of Random Prostate Biopsies Prompted by Isolated PSA Elevation in Subjects Referred to an Outpatient Biopsy Facility in a Routine Clinical Scenario

Abstract

To assess the validity of PSA doubling time (PSADT) as a predictor of prostate sextant biopsy outcome in patients with PSA levels in the 4-10 ng/mL range. A consecutive series of 355 sextant biopsies performed during 2001-2007 in subjects with negative digital rectal examination and transrectal ultrasonography was considered. Variables tested as possible predictors were age, total and free/total PSA value, PSA velocity and PSA doubling time. While PSA at time of biopsy and free/total PSA were determined with a standardized method undergoing strict quality control, previous PSA values used to assess velocity/doubling time came from other labs using different assays over widely varying intervals of time. The association with biopsy outcome (cancer vs non-cancer) was investigated by univariate and multivariate analysis. Apart from free/total PSA ratio, no other studied variable showed a statistically significant and independent association with biopsy outcome, either at univariate or multivariate analysis. No studied variable had a good performance as a biopsy indicator. Depending on the variable considered, 1.17 to 1.97 cancers would be missed to spare 10 benign biopsies. When based on PSA data determined with different assays over widely varying intervals and in the absence of an underlying protocol for PSA surveillance, PSA velocity and doubling time should never discount a biopsy prompted by total PSA elevation.