Effect of prostate volume on tumor grade in patients undergoing radical prostatectomy in the era of extended prostatic biopsies.

ABSTRACT

PURPOSE: We investigated the influence of prostate volume on biopsy and prostatectomy Gleason score, the incidence of upgrading and total tumor volume. MATERIALS AND METHODS: From 1997 to 2004, 247 patients were diagnosed with prostate cancer by multisite extended prostatic biopsy (10 or 11 cores) and underwent radical prostatectomy at our institution without neoadjuvant therapy. Medical records were reviewed to determine patient age at diagnosis, preoperative prostate specific antigen, prostate volume, clinical stage, biopsy Gleason score, pathological stage, prostatectomy Gleason score and total tumor volume. The Mann-Whitney and chi-square tests were used to compare variables among groups and multivariate regression analysis was used to determine predictors of Gleason score. RESULTS: Median patient age was 61 years and median preoperative prostate specific antigen was 5.5 ng/ml. Median prostate volume on transrectal ultrasound was 37 cc. Prostatectomy Gleason score was 6 in 31% of cases, 7 in 57% and 8-9 in 12%. Prostate volume greater than 50 cc was significantly associated with a higher incidence of well differentiated tumors (Gleason score 6) at prostatectomy, that is 17.9% in patients with a prostate volume of 25 cc or less, 28.9% in those with a prostate volume of 25 to 50 cc and 45.3% in those with a prostate volume of greater than 50 cc (p<0.01). In addition, the incidence of tumor upgrading was significantly lower in patients with a large prostate volume (greater than 50 cc) compared to that in those with a smaller prostate volume (20.8% vs 36.1%, p<0.05), particularly in the subset with biopsy Gleason score 6 (24% vs 54.1%, p<0.01). Patients with a large prostate volume (greater than 50 cc) had smaller total tumor volume with a trend toward statistical significance (median total tumor volume 0.86 vs 1.1 cc, p=0.0631). CONCLUSIONS: In the era of extended prostatic biopsies patients with a large prostate volume have a significantly higher incidence of well differentiated tumor at prostatectomy and a lower likelihood of tumor upgrading.