Extraprostatic Extension Is Extremely Rare for Contemporary Gleason Score 6 Prostate Cancer.

Background: A significant proportion of men with Gleason score 6 (GS6) prostate cancer undergo treatment with radiation or surgery.

Objective: To assess pathologic stage of pure GS6 at radical prostatectomy (RP).

Design, Setting, And Participants: In the period 2003-2014, 7817 patients underwent RP at two institutions. Of 2502 patients with GS6 at surgery, 60 were identified as stage pT3a-b on initial pathologic review, 55 with pT3a (extraprostatic extension, EPE), and five with pT3b (seminal vesicle invasion; SVI). All cases of GS6 with pT3 disease underwent contemporary pathologic evaluation for Gleason grade, stage, and extent of EPE. At one institution, all GS≥7 pT3b cases were re-reviewed for downgrading. The 2014 International Society of Urological Pathology (ISUP) Gleason grading criteria and 2009 ISUP recommendations on pT3 staging were applied.

Outcome Measurements And Statistical Analysis: Calculated incidence (%) of pT3a, pT3b, pT4, and lymph node-positive disease.

Results And Limitations: Of the 60 GS6 pT3a-b cases identified in the period 2003-2014, seven (0.28% of entire GS6 cohort) with GS6 and pT3a were identified after re-review, all focal EPE. Among the re-examined cohort, no cases of GS6 with pT3b were observed. None of the 132 GS≥7 pT3b cases were downgraded to GS6. Limitations include partial embedding of specimens and separate pathologic review at each institution.

Conclusions: In a large prostatectomy cohort, GS6 never had seminal vesicle invasion (0%) and was very rarely (0.28%) associated with extraprostatic extension.

Patient Summary: GS6 prostate cancer rarely spreads outside the prostate. A new finding in this study was that GS6 prostate cancer never spread to the seminal vesicles.