The Impact of Downgrading from Biopsy Gleason 7 to Prostatectomy Gleason 6 on Biochemical Recurrence and Prostate Cancer Specific Mortality

Abstract

Purpose: Gleason score is one of the most important prognostic indicators for prostate cancer. Downgrading from biopsy Gleason score 7 to radical prostatectomy Gleason score 6 occurs commonly and yet to our knowledge the impact on survival outcomes is unknown. We examined biochemical recurrence and prostate cancer specific mortality risk in a large cohort evaluated by a single group of expert urological pathologists.

Materials and methods: Of 23,918 men who underwent radical prostatectomy at our institution between 1984 and 2014, 10,236 with biopsy and radical prostatectomy Gleason score 6 or 7 without upgrading were included in analysis. The cohort was divided into 3 groups, including group 1-biopsy and radical prostatectomy Gleason score 6 in 6,923 patients (67.6%), group 2-Gleason score 7 downgraded to radical prostatectomy Gleason score 6 in 648 (6.3%) and group 3-biopsy and radical prostatectomy Gleason score 7 in 2,665 (26.0%). Biochemical recurrence and prostate cancer specific mortality risks were compared using Cox regression and competing risk analyses adjusting for clinicopathological variables.

Results: At a median followup of 5 years (range 1 to 29), 992 men experienced biochemical recurrence and 95 had died of prostate cancer. Biochemical recurrence-free survival in downgraded cases (group 2) was better than in group 3 cases, which had Gleason score 7 on biopsy and radical prostatectomy (p <0.001), but worse than group 1 cases, which had Gleason score 6 on biopsy and radical prostatectomy (p <0.001). Downgrading was independently associated with biochemical recurrence (adjusted HR 1.87, p <0.0001) but not with prostate cancer specific mortality (adjusted HR 1.65, p = 0.636).

Conclusions: Downgrading from biopsy Gleason score 7 to radical prostatectomy Gleason score 6 was an independent predictor of biochemical recurrence but not prostate cancer specific mortality, likely due to the presence of minor amounts of Gleason pattern 4.

Keywords: biopsy; mortality; neoplasm grading; prostatectomy; prostatic neoplasms.