Prostate biopsy and radical prostatectomy Gleason score correlation in heterogenous tumors: proposal for a composite Gleason score.

When prostate biopsy cores are separately identified in multiple containers, current recommendations are to grade each specimen individually. For treatment algorithms, the highest Gleason score (HGS) is typically used as the overall score, even if a lower score predominates. This practice has the potential to misrepresent the overall cancer in the entire gland for some patients and place them in a higher-grade group. We compare a novel composite Gleason score (CGS), integrating grade patterns from contiguous positive biopsy sites, with HGS to determine correlation with the radical prostatectomy (RP) Gleason score (GS). One hundred needle biopsy cases from 2008 to 2012 with >2 GSs in a biopsy set (eg, 3+3=6, 3+4=7, and 4+3=7) or more than a 1-step difference in GS (eg, 3+4=7 and 4+4=8 without 4+3=7) were analyzed. Grades were assigned using both methods (HGS and CGS) and compared with RPGS. Grade groups I to V were used to define downgrade and upgrade. Comparing HGS with RPGS, 31% remained the same and 69% had a change in GS (87% downgraded and 13% upgraded). Comparing CGS with RPGS, 59% remained the same and 41% had a change in GS (10% downgraded and 90% upgraded). Of the 2 methods, the CGS showed better overall correlation with RP (P<0.001) and was less likely to be downgraded compared with HGS. CGS correlates better with RPGS than HGS when >2 grades are present in a biopsy set. CGS has a significantly lower rate of downgrade and predicts the RPGS more accurately than HGS.

Does discontinuous involvement of a prostatic needle biopsy core by adenocarcinoma correlate with a large tumor focus at radical prostatectomy?

When prostate needle biopsies are involved discontinuously by tumor, no consensus remains on the optimal method of tumor quantification. We investigated whether discontinuous biopsy involvement usually results from a large tumor focus or multiple small foci. Prostate needle biopsies with discontinuous tumor and corresponding whole-mounted radical prostatectomies from 2008 to 2013 were analyzed. Linear length and percentage of biopsy involvement were measured both including and subtracting the benign intervening tissue. The corresponding region of the prostatectomy specimen was evaluated for tumor size and multifocality. From over 800 biopsy sets and 400 prostatectomies performed annually, 40 patients met inclusion criteria. Excluding benign tissue, length and percentage of biopsy involvement ranged from 1 to 7 mm and 5% to 66% (median 2.5 mm, 20%), whereas including intervening tissue yielded 4 to 15.5 mm and 25% to 100%, (median 7 mm, 70%), respectively. Benign intervening tissue measured from 2 to 10.5 mm (median 3.5 mm). In 31 patients (78%), a single tumor focus was present in the corresponding region of the prostate (the dominant tumor in 25/31). In 9 patients, multiple small foci were present. Eleven patients could have been excluded from active surveillance eligibility by measuring tumor from end to end (>50% involvement), of whom only 1 met criteria for clinically insignificant cancer at prostatectomy. Discontinuous tumor in a prostate biopsy often results from a single tumor focus in the corresponding region of the prostate (78%). Therefore, we recommend that an end-to-end measurement be provided, with accompanying diagnostic comment that this often correlates with the size of a single tumor focus.