Gleason Misclassification Rate is Independent of Number of Biopsy Cores in Systematic Biopsy.

OBJECTIVE - To compare the utility of saturation core biopsy and twelve-core biopsy in detecting true Gleason grades, using final pathology in prostatectomy specimens as outcome measures, with a particular interest in Gleason upgrading.

MATERIALS AND METHODS - We compared the concordance rates of Gleason grades diagnosed on biopsies and prostatectomy specimens in 375 consecutive patients, including 106 saturation biopsies (18-33 cores, median=20 cores) and 269 twelve-core biopsies. Grading bias was addressed by a central re-review of all cases that had discordance in reporting high Gleason grades (Gleason grade ≥ 4) on biopsies and prostatectomy specimens.

RESULTS - For patients with high Gleason grades on final pathology, saturation and twelve-core biopsy schemes had a comparable sensitivity, specificity, negative and positive predictive values (72.5% vs 69.5%, 91.9% vs 97.6%, 64.2% vs 58.4%, and 94.3% vs 98.5%, respectively) in detecting high Gleason grades. On multivariate analysis, pre-biopsy serum PSA and clinical T stage independently predicted Gleason upgrading; saturation biopsy was not a significant predictor. Approximately one third of cases where high Gleason grade was not present in the biopsy were attributed to the confinement of high grade tumors to unusual anatomic locations such as anterior lobes, apex, bladder neck, and para-sagittal zones.

CONCLUSIONS - Our study showed that Gleason misclassification rate is independent of the number of biopsy cores in systematic biopsy. One of the reasons for missing high Gleason grade tumors on systematic biopsy was unusual tumor location outside of the biopsy grid, supporting the need for improved detection technique such as MRI-guided targeted biopsies.

Urology. 2016 Mar 01 [Epub ahead of print]

Liza Quintana, Ashley Ward, Sean J Gerrin, Elizabeth Genega, Seymour Rosen, Martin G Sanda, Andrew A Wagner, Peter Chang, William C DeWolf, Huihui Ye

Department of Pathology, Harvard Medical School, Boston, MA., Department of Pathology, Harvard Medical School, Boston, MA., Department of Pathology, Harvard Medical School, Boston, MA., Department of Pathology, Tufts Medical Center, Boston, MA., Department of Pathology, Harvard Medical School, Boston, MA., Department of Urology, Emory University School of Medicine, Atlanta, GA., Division of Urologic Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA., Division of Urologic Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA., Division of Urologic Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA., Department of Pathology, Harvard Medical School, Boston, MA.