Impact of the percentage of positive biopsy cores on the further stratification of primary grade 3 and grade 4 Gleason score 7 tumors in radical prostatectomy patients

Objectives. To examine whether the percentage of core biopsies positive can further stratify Gleason score 7 patients with primary Gleason grade into precise prognostic groups. Methods. Between 1991 and 1999, 379 radical prostatectomy patients were found to have pathologic Gleason 7 tumors. The patients were divided into primary grade 3 or 4. Percentage positive was calculated by dividing the number of positive core biopsies by the total number of cores. Results. In the cohort, 290 tumors were primary grade 3, and 89 were primary grade 4. On univariate analysis patients with primary grade 3 tumors had a significant prostate-specific antigen (PSA) progression-free survival advantage over grade 4 patients. When separated according to percentage of core biopsies positive, statistical analysis revealed significantly better 60-month actuarial PSA progression-free survival for patients with grade 3 and grade 4 and less than 50% core biopsies positive as compared with grade 3 and grade 4 and 50% or more core biopsies positive (85%, 85%, 61%, and 33%, respectively). Furthermore, multivariate analysis demonstrated that primary grade did not have an independent impact on biochemical progression-free survival. However, on subset analysis, among patients with 50% or more biopsy cores positive, primary Gleason grade was indeed found to have a significant, independent impact. Conclusions. In the present study Gleason 7 patients with primary grade 4 tumors and less than 50% of biopsy cores positive had an excellent prognosis after radical prostatectomy. Our data suggest that among Gleason 7 patients, the percentage of positive biopsies is a stronger predictor of biochemical progression-free survival than primary Gleason grade.