Background: Standard 6-core prostate biopsy accurately predicts the Gleason score of radical prostatectomy specimens 50-60% of the time. We review the accuracy of standard 6-core and extended 12-core prostate biopsy in predicting radical prostatectomy specimen pathology and tumor laterality at our institution from 1998-2005.
Methods: 547 radical prostatectomies were performed after standard 6-core or extended 12-core biopsy which had pathologic data sufficient for analysis. Preoperative Gleason sum and tumor location were compared to radical prostatectomy specimen Gleason sum and tumor location. Statistical analysis was performed using Chi-square test and Fisher’s exact test. Institutional review board approval was obtained prior to initiation of the study.
Results: 278 (51%) patients underwent standard 6-core biopsy and 269 (49%) patients underwent extended 12-core biopsy prior to radical prostatectomy. The agreement between biopsy Gleason sum and radical prostatectomy Gleason sum was 175 of 278 (63%) for standard biopsy and 196 of 269 (73%) for extended biopsy (Fisher’s exact test p <0.02). Final pathological Gleason sum was higher in 78 of 278 (28%) and 50 of 269 (18.6%) and lower in 25 of 278 (9%) and 23 of 269 (8.6%) for standard 6-core and extended 12-core biopsy respectively (chi square test p < 0.03). For tumor laterality analysis, 230 standard 6-core biopsies and 240 extended 12-core biopsies were analyzed. Biopsy correctly predicted tumor laterality in 44.5% and 46.5% of cases for standard 6-core and extended 12-core biopsy respectively.
Conclusions: Extended 12-core prostate biopsy confers a modest but stastically significant improvement in predicting radical prostatectomy Gleason sum. Both modalities correctly predicted tumor laterality in less than 50% of cases.