Diagnostic gleason sums frequently differ from those determined by pathologic analysis of prostate biopsy specimens, a study shows. The discrepancies were due mostly to understaging.

Researchers at the Duke Prostate Center (DPC), Duke University Medical Center in Durham, N.C., studied diagnostic and pathologic Gleason sums in 2,963 patients who underwent radical prostatectomy from 1988 to 2006.

Overall, diagnostic Gleason sums did not correlate with those of pathologic analysis in 55.8% of cases, the investigators reported at the Society of Urologic Oncology annual meeting in Bethesda, MD. Diagnostic Gleason sums were un-derstaged in 41.9% of cases and overstaged in 13.9%. Understaging accounted for 75.1% of the Gleason sum discrepancies.

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The investigators, led by Judd W. Moul, MD, professor of urology and chief of the Division of Urologic Surgery and Duke Prostate Center, also found that age and PSA values were associated with discrepancies in diagnostic and pathologic Gleason sums. Compared with men younger than 50 years, men over age 60 were four times more likely to have biopsy Gleason sums understaged.

Compared with men who had a PSA level below 10 ng/mL, those with a PSA level of 10-20 and greater than 20 ng/mL had a two- and threefold greater likelihood of having their biopsy Gleason sums understaged.In addition, the study showed that the lower the diagnostic Gleason sum, the higher the probability of understaging.

“Advanced age and high PSA were predictive of diagnostic Gleason sum understaging, indicating a need to adjust our biopsy strategy for older men and men with high PSA,” the investigators concluded.
The study revealed that the proportion of diagnostic and pathologic Gleason sums that show discrepancy has declined over time, from 58.6% in the period 1988-1999 to 49.3% in the period 2000-2006. This decline may be due to the use of extended core biopsy protocols in recent years that have been shown to boost cancer detection rates and staging accuracy, the investigators explained.
During those two periods, diagnostic understaging decreased from 42.9% to 39.5% and overstaging decreased from 15.7% to 9.8%.  These findings indicate that surgical treatment is the only current way to verify discrepancies, Dr. Moul noted. “For men who choose nonsurgical treatment such as radiation therapy or cryotherapy…age and PSA levels are the variables to use to estimate the probabilities of understaging during decision-making process and outcome prediction,” he said.
Discrepancies, the authors ex-plained, are caused by human and sampling errors during biopsy and pathologic examination. The ideal solution, they stated, is to eliminate sampling errors by developing a novel prostatic biopsy technique that is tumor-targeted and can distinguish biologically aggressive tumor cells from indolent ones.
Dr Moul’s co-investigators included Brandon Isariyawongse, BA, Leon Sun, MD, PhD, Thomas Polascik, MD, Craig Donatucci, MD, Kelly Maloney, MD, David Albala, MD, John Madden, MD, Lionel Banez, MD, Vladimir Mouraviev, MD, and Cary Robertson, MD.