Department of Radiation Oncology, Brigham and Women's Hospital and Dana-Farber Cancer Institute, Boston, MA.
Prostate-specific antigen (PSA) velocity, like PSA level, can be confounded. In this study, we estimated the impact that confounding factors could have on correctly identifying a patient with a PSA velocity >2 ng/ml/y.
Between 2006 and 2010, a total of 50 men with newly diagnosed PC comprised the study cohort. We calculated and compared the false-positive and false-negative PSA velocity >2 ng/ml/y rates for all men and those with low-risk disease using two approaches to calculate PSA velocity. First, we used PSA values obtained within 18 months of diagnosis; second, we used values within 18 months of diagnosis, substituting the prebiopsy PSA for a repeat, nonconfounded PSA that was obtained using the same assay and without confounders.
Using PSA levels pre-biopsy, 46% of all men had a PSA velocity >2 ng/ml/y; whereas this value declined to 32% when substituting the last prebiopsy PSA for a repeat, nonconfounded PSA using the same assay and without confounders. The false-positive rate for PSA velocity >2 ng/ml/y was 43% as compared with a false-negative rate of PSA velocity >2 ng/ml/y of 11% (p = 0.0008) in the overall cohort. These respective values in the low-risk subgroup were 60% and 16.7% (p = 0.09).
This study provides evidence to explain the discordance in cancer-specific outcomes among groups investigating the prognostic significance of PSA velocity >2 ng/ml/y, and highlights the importance of patient education on potential confounders of the PSA test before obtaining PSA levels.
Written by:
Park JJ, Chen MH, Loffredo M, D'Amico AV. Are you the author?
Reference: Int J Radiat Oncol Biol Phys. 2011 Jun 1. Epub ahead of print.
doi: 10.1016/j.ijrobp.2011.04.019
PubMed Abstract
PMID: 21640512
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