摘要：Purpose Nonrepresentative biopsy sampling of prostate cancers with a biopsy Gleason score of 8 can adversely influence decisions regarding androgen deprivation in men receiving primary radiation therapy. The frequency of and factors associated with downgrading Gleason 8 biopsies at prostatectomy are not well known. Materials and Methods We used records from NCDB (National Cancer Database), a hospital based registry in the United States, of 72,556 men with prostate cancer diagnosed from 2010 to 2013, including 5,474 with Gleason 8 biopsies and no other high progression risk criteria according to NCCN (National Comprehensive Cancer Network®) Guidelines®. The prevalence of Gleason 8 downgrading was calculated. Generalized estimating equation multivariable regression models were used to estimate the prevalence ratios and 95% CIs of downgrading by demographic and clinical factors, and evaluate the association of Gleason 8 downgrading with cT (clinical T) to pathological T category up staging. Results Of 5,474 Gleason 8 biopsies in men lacking other high progression risk criteria 3,263 (60%) were downgraded, changing the progression risk category from high to intermediate. A higher prevalence of Gleason 8 downgrading was significantly and independently associated with decreasing age, African American race, lower cT category, lower prostate specific antigen quartile and certain combinations of primary and secondary Gleason grades (3 + 5 greater than 4 + 4 greater than 5 + 3). Gleason 8 downgrading in cases of cT less than 3 was independently and significantly associated with a lower prevalence of up staging (prevalence ratio = 0.65, 95% CI 0.61–0.69). Conclusions Downgrading Gleason 8 biopsies is common. Patient evaluation based on Gleason 8 biopsies often results in overestimating progression risk and disease extent, which may lead to overtreatment.