Performance Of Prostate Specific Antigen For Predicting Prostate Cancer Is Maintained After A Prior Negative Prostate Biopsy

Main Category: Prostate / Prostate Cancer
Also Included In: Urology / Nephrology;  Cancer / Oncology
Article Date: 31 Jul 2008 - 3:00 PDT

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UroToday.com - In the August 2008 issue of the Journal of Urology, Dr. Ian Thompson and colleagues explored the performance characteristics of PSA after a previous negative prostate biopsy. The population of men had all undergone prostate biopsy regardless of PSA or digital rectal examination (DRE) findings, thus minimizing the confounding effects of verification bias.

The investigators studied the Prostate Cancer Prevention Trial database of 18,882 randomized men with a normal DRE and a PSA of 3.0ng/ml or less who were treated with either finasteride or placebo. If a biopsy was not performed for indication during the study, after 7 years, participants without a prior cancer diagnosis were recommended to undergo prostate biopsy. The men from the placebo group of the study who had only one biopsy, or a first and second prostate biopsy during the study, and a PSA and DRE within one year before each biopsy, were used to compare the performance of PSA for predicting outcomes.

In the placebo arm of the Prostate Cancer Prevention Trial, 4,291 men had a first and only prostate biopsy during the study with DRE and PSA within 1 year before it. An additional 687 men had a negative first biopsy and underwent a second one during the study. Among men with 2 biopsies, a statistically significantly greater number of the first biopsies (87.5%) were prompted by increased PSA or abnormal DRE, than the second (47%), but this result is largely driven by the design of the PCPT. Average PSA values did not statistically differ between the first biopsy and the second. Sensitivity and specificity for clinical cutoffs of PSA for first and second biopsy obviously varied with the stringency of the cutoff selected. PSA cutoff needs to be increased at the second biopsy to obtain the same false-positive rate and subsequent similar true positive rate as the first biopsy. The C-statistic was 0.650 for the first biopsy and 0.664 for the second biopsy. Thus the second biopsy C-statistic was greater that 0.5 demonstrating that PSA does not lose predictive value for the detection of prostate cancer even following an initial, negative biopsy.

Thompson IM, Tangen CM, Ankerst DP, Chi C, Lucia MS, Goodman P, Parnes H, Coltman CA Jr.
J Urol. 2008 Jun 10. Epub ahead of print.
doi:10.1016/j.juro.2008.04.01

Reported by UroToday.com Contributing Editor Christopher P. Evans, MD, FACS

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