Background:
Differentiation between a Gleason score (GS) of 6 and 7 in prostate biopsy (Pbx) is important for treatment decision-making. Nevertheless, under-grading errors compared with the actual pathologic grade at radical prostatectomy (RP) are common. We compared the characteristics and outcomes of tumors that were scored 6 on Pbx but were 7 at the subsequent RP pathology to tumors with a consistent rating of either GS6 or GS7 at both biopsy and surgery.
Methods:
Retrospective database analysis from our referral center (1989-2004). We compared pre-prostatectomy characteristics, RP pathological features and PSA failure rate (defined as any 2 consecutive, detectable PSA levels), for 3 subgroups of patients: matched GS6 (Pbx to RP) (n=156), upgraded GS6/7 (PbxGS6, RP GS7, (n=205), or matched GS7 (Pbx GS7, RP GS7, n=412). All the biopsy/RP pathology specimens were reviewed by our institutional uro-pathologists. Mean number of biopsy cores was 9 in all 3 subgroups of patients.
Results:
The RP Gleason score matched the Pbx score in 38.2% of Pbx GS6 and 81.4% of Pbx GS7. Higher PSA levels and increased percent of cancer in the Pbx were associated with discordance between Pbx/RP GS. Margin (p = 0.0075) or seminal vesicle involvement (p = 0.0002), cancer volume (p < 0.001) and PSA failures rates (p=0.014) were significantly higher in the under-graded GS7 cancers as compared to the matched GS6 cases, but comparable to those with matched GS7 tumor grade (p=0.66)
Conclusions:
Nearly half of tumors graded as GS6 at biopsy are GS7 at surgery. Upgraded GS6/ GS7have similar outcomes as genuine GS7 cancers. These findings should be considered when assessing outcome data from treatments other than RP.

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