upgrading the gleason score in extended prostate biopsy implications for treatment choice purpose to determine the incidence of overestimation of gleason score gs in extended prostate biopsy and consequently circumventing unnecessary aggressive treatmentmethods and materials this is a retrospective study of 464 patients who underwent prostate biopsy and radical prostatectomy between january 2001 and november 2007 the gs from biopsy and radical prostatectomy were compared the incidence of overestimation of gs in biopsies and tumor volume were studied multivariate analysis was applied to find parameters that predict upgrading the gs in prostate biopsyresults the exact agreement of gs between prostate biopsy and radical prostatectomy occurred in 569 of cases in 291 cases it was underestimated and it was overestimated in 14 one hundred and six 228 patients received a diagnosis of high gs 8 9 or 10 in a prostate biopsy in 292 of cases the definitive gleason score was 7 or lower in cases in which gs was overestimated in the biopsy tumors were significantly smaller in multivariate analysis the total percentage of tumor was the only independent factor in overestimation of gs tumors occupying less than 33 of cores had a 56fold greater chance of being overestimatedconclusion in the extended biopsy era and after the international society of urological pathology consensus on gs almost one third of tumors considered to have high gs at the biopsy may be intermediaterisk cancers in that condition tumors are smaller in biopsy this should be remembered by professionals involved with prostate cancer to avoid overtreatment and undesirable side effects