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19-03-2013 | Surgery | Article

Improved approach to biopsy decisions in prostate cancer


Free abstract

medwireNews: Researchers have developed a strategy for reducing the number of initial biopsies performed among men who are at low risk for prostate cancer.

Performing prebiopsy multiparametric magnetic resonance imaging (MRI) along with assessment of prostate volume identified men who could avoid biopsy, with a low likelihood of missing significant cancer, report Noboru Numao (Tokyo Medical and Dental University Graduate School, Japan) and colleagues.

In a study of 351 men with a prostate specific antigen (PSA) level between 2.5 and 20 ng/mL and/or a digital rectal examination (DRE) indicating possible clinically localized disease, all participants underwent prebiopsy multiparametric MRI comprising T2-weight imaging, diffusion-weighted imaging, and/or dynamic contrast-enhanced imaging. Within 3 months of MRI, the men also underwent extended biopsy. The number of sampling cores taken ranged from 14 to 29, with a mean of 21 cores.

On dividing the cohort into low-risk (PSA <10 ng/mL, normal DRE) and high-risk (PSA ≥10 ng/mL, abnormal DRE) groups, the researchers found that the positive MRI rate was significantly lower in the low-risk than the high-risk group, at 38% versus 59%.

In addition, men with a negative MRI in the low-risk group had a substantially lower frequency of significant cancer (as defined by Gleason score and cancer volume), compared with men from the same group who had a positive MRI result and compared with all men in the high-risk group.

In order to identify men who could avoid biopsy while remaining at a low risk for nondetection of significant cancer, the team performed multivariate analysis for the men from the low-risk group who had negative MRI results.

As reported in the Journal of Urology, prostate volume was the only significant predictor for significant cancer in this group.

Further analysis showed that, in the low-risk group, the negative predictive value of a combination of positive MRI and lower prostate volume (less than 33 mL) for significant cancer was 95.1%-97.5%.

"At this PPV [positive predictive value], 33% of men could avoid biopsy," note Numao and colleagues.

Currently, the diagnostic strategy for prostate cancer does not generally include MRI before initial biopsy due to the associated financial and physical burdens, explain the researchers. "However, if numerous biopsies could be avoided through the use of prebiopsy MRI, as we have shown, the burdens would be eliminated."

By Sally Robertson, medwireNews Reporter

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