Prostate Biopsy and Radical Prostatectomy Gleason Score Correlation in Heterogenous Tumors

Abstract

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.

Recent advances in prostate cancer pathology: Gleason grading and beyond

“…Arias‐Stella et al recently proposed a composite GS which integrates grade patterns from contiguous positive biopsy sites. Composite GS correlated better with RP GS than the highest biopsy GS . Specifically, the former was less likely to be downgraded compared with the latter in RP specimens.…”

Contemporary prostate biopsy reporting: insights from a survey of clinicians’ use of pathology data

“…When tumour foci are widely separated, this should be clearly stated in the pathology report (eg, 10 mm (discontinuous)). Arias-Stella et al studied a small series of 40 cases and reported that discontinuous biopsy involvement more commonly reflects a large tumour focus (78%) than multiple small foci (22%) 16. There is no consensus on how widely separated the cancer glands should be to categorise the tumour as ‘discontinuous’.…”

“…There is no consensus on how widely separated the cancer glands should be to categorise the tumour as ‘discontinuous’. Arias-Stella et al used a cut-off of 2 mm as this corresponds to approximately an entire ×10 magnification microscopic field lacking cancer glands 16. However, as in the case of Gleason grading, pathologists should also factor in tumour morphology when determining linear tumour extent in a prostate biopsy.…”

Gleason score assignment is the sole responsibility of the pathologist

“…All these previous studies relate to patient cohorts, and may not be applicable to individual patients, because biopsy GS provides only an estimate of the GS in the prostate due to sampling variation, regardless of the methodology used to assign the GS . In a large series of 15 598 radical prostatectomy specimens, 22% of patients with biopsy GS 4 + 4 were found to have primary pattern 3 (3 + 3/3 + 4) on radical prostatectomy .…”

“…All these previous studies relate to patient cohorts, and may not be applicable to individual patients, because biopsy GS provides only an estimate of the GS in the prostate due to sampling variation, regardless of the methodology used to assign the GS. 6,[9][10][11] In a large series of 15 598 radical prostatectomy specimens, 22% of patients with biopsy GS 4 + 4 were found to have primary pattern 3 (3 + 3/3 + 4) on radical prostatectomy. 9 Given the sampling error of the biopsy technique, it is unlikely that a patient with a biopsy GS7 (3 + 4)/grade group 2 with only a minor component of pattern 4 would have a worse outcome just because one of the cores happened to have an exclusive small component of pattern 4 cancer.…”