Extended prostate biopsy scheme improves reliability of Gleason grading: implications for radiotherapy patients

With sextant prostate biopsies, there is up to a 1-in-3 chance that the underlying pathologic Gleason grade is higher. Knowledge of the underlying grade might have significantly altered the therapeutic recommendations and management for patients electing radiotherapy for localized prostate cancer (e.g., eligibility for brachytherapy, androgen suppression with external beam radiotherapy, elective pelvic radiotherapy). This study examines the concordance patterns between biopsy and matched radical prostatectomy Gleason grade among patients undergoing an extended 10-core biopsy scheme to assess its reliability compared to sextant biopsies.

Seventy-eight consecutive patients underwent an extended 10-core peripheral zone biopsy scheme (sextant plus two lateral mid and two lateral base biopsies) and subsequent radical prostatectomy at this institution between mid-2000 and mid-2003. No patient received androgen suppression. All histologic grading were made by a single pathologist (J.E.M.). Needle biopsies were characterized for location, linear involvement of cancer within positive cores, and total number of positive cores. Radical prostatectomy specimens were step-sectioned at 3-mm intervals and were characterized for total cancer volume and percentage of each Gleason grade present. Clinical parameters available included digital rectal exam, preoperative PSA, and ultrasound prostate volume. A "clinically significant" upgrading of the biopsy was defined as any of the following: (1) a biopsy Gleason score (bGS) of 6 to a pathologic GS (pGS) of 7 or higher, (2) a bGS 3 + 4 to a pGS of 4 + 3 or higher, and (3) a bGS of 7 to a pGS of 8 or higher. Statistical analyses were performed on the patterns Gleason score concordance between biopsies and matched radical prostatectomies.

An exact Gleason score match between biopsy and prostatectomy was observed in 62% of patients using the sextant biopsy scheme (SB), an upgrading of 1 or more grade points was seen in 25% and a downgrading of 1 or more points in 13% for SB. These rates of grade discordance are comparable to those of published sextant series. An exact match using the extended biopsy scheme (EB) was 63% (p = 0.61 compared with SB), whereas upgrading was 13% (p = 0.045 compared with SB) and downgrading was 24% (p = 0.06 compared with SB). A "clinically significant" upgrading as defined here was present in 38.1% of the SB group compared with 23.1% of the EB group (p = 0.039). For patients with bGS of 6, a clinically significant upgrading occurred in 66.7% with SB and in 36.8% with EB (p = 0.068). Upgrading of the primary Gleason grade from 3 to 4/5 was seen in 41.8% for the SB and in 25.5% for the EB group (p = 0.078). No clinical factors (T-stage, PSA, prostate volume, % positive cores, linear extent of cancer) were found to predict for a clinically significant upgrading of biopsies on logistic regression analysis.

The extended 10-core biopsy scheme significantly improves on sextant biopsies in predicting the underlying pathologic Gleason score for prostate cancer. In particular, it is superior to sextant biopsies in revealing the presence of an underlying high-grade component. The potential clinical impact this improvement has for patients ultimately selecting radiotherapy suggests that an extended biopsy scheme should become the standard of care. Nevertheless, even with this improvement, there still remains up to a 1-in-5 chance that the underlying grade will be higher.