Saturation prostate biopsy does not increase the likelihood of detecting high Gleason grade tumors, according to a new study.
Unusual tumor location outside of biopsy grids, such the anterior lobes, apex, bladder neck, and para-sagittal zones, is among the main reasons for missing high Gleason grade tumors, a finding that supports the need for improved detection methods, such as magnetic resonance imaging (MRI)-guided targeted biopsy, a research team led by Huihui Ye, MD, of Beth Israel Deaconess Medical Center in Boston, reported.
Dr. Ye's group compared the diagnostic accuracy of the standard 12-core prostate biopsy and saturation biopsy (18–33 cores, median 20) among 375 consecutive patients who underwent radical prostatectomy (RP). Of these, 269 had 12-core biopsies and 106 had saturation biopsies. The researchers compared biopsy findings with final pathologic findings of RP specimens.
A similar proportion of patients in the 12-core and saturation biopsy groups had high Gleason grade prostate cancer (PCa) on biopsy (49.1% vs. 50%) at RP (69.5% vs. 65.1%).
Among patients with high Gleason grades on final pathology, the 12-core and saturation biopsy schemes had comparable sensitivity, specificity, and negative and positive predictive values (69.5% vs. 72.5%, 97.6% vs. 91.9%, 58.4% vs. 64.2%, and 98.5% vs. 94.3%, respectively) in detecting high Gleason grades, the investigators reported online ahead of print in Urology. On multivariate analysis, pre-biopsy serum PSA level and clinical T stage (cT2 vs. cT1) independently predicted Gleason upgrading. Saturation biopsy was not a significant predictor.
Dr. Ye and colleagues pointed out some study limitations, including the use of data from a single tertiary-care academic hospital in which men with PCa were most treated by 4 urologists. “Therefore, our study results may not be representative of other urological practices, particularly private practice and community hospitals,” the researchers noted. In addition, the saturation biopsy approach was performed by a single urologist, whereas 12-core biopsies were performed by multiple urologists. “The operator factor could lead to differences in biopsy core quality,” the authors cautioned.
The investigators defined a Gleason upgrade as the presence of high-grade tumors in RP specimens who had Gleason 3 disease only on biopsy. They defined a Gleason downgrade as final pathology of Gleason 3 disease only on RP specimens from patients who had high-grade tumors diagnosed on biopsy.
The 12-core biopsy and saturation biopsy groups were similar with respect to median age at PCa diagnosis (60 vs. 59 years). Compared with the saturation group, the 12-core group had a significantly higher proportion of African American patients than the saturation group (19.3% vs. 6.6%), a significantly higher median pre-biopsy PSA level (5.4 vs. 4.6 ng/mL), and a significantly higher proportion of patients with cT2 tumors (26.6% vs. 12.3%). The median prostate volume was significantly higher in the saturation than the 12-core group (42 vs. 36 mL).
“The authors are to be congratulated for their unexpected but clinically important findings,” commented Judd W. Moul, MD, the James H. Semans, MD, Professor of Surgery at Duke University Medical Center in Durham, N.C., who was not part of the new study but has conducted research looking at the correlation between biopsy and pathologic Gleason sums.
Over the past few years, multiple studies have shown that about 40% of men thought to have Gleason 6 cancer on initial biopsy are upgraded if they undergo radical prostatectomy, said Dr. Moul, who also is director of the Duke Prostate Center. The new study found that the Gleason misclassification rate was about 40% regardless of whether patients had the standard 12-core or saturation biopsy. “The authors use these data to suggest that prostate MRI may improve the selection for active surveillance,” Dr. Moul said. “However, prostate MRI has yet to be proven prospectively to help improve the care of our surveillance patients.”
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