Prostate needle biopsies: multiple variables are predictive of final tumor volume in radical prostatectomy specimens

Tumor volume is one of the most powerful predictors of patient outcome in prostatic adenocarcinoma. It is uncertain as to which preoperative variables are most predictive of final tumor volume at radical prostatectomy, especially among patients who have had positive biopsies at multiple biopsy sites. The current study attempted to identify the biopsy variables that are most predictive of final tumor volume.

The authors examined prostate biopsy specimens from 151 consecutive patients with at least 2 positive biopsy sites. The following data were collected: highest percentage of adenocarcinoma at any biopsy site, percentage of adenocarcinoma at the biopsy site with the highest Gleason score, highest percentage of cores positive for adenocarcinoma at any biopsy site, percentage of positive cores with carcinoma at the site with the highest Gleason score, number of positive sites, tumor bilaterality, and percentage of biopsy sites positive for disease. All patients underwent radical prostatectomy. The prostatectomy specimens were entirely embedded and whole mounted. Tumor volume was measured using the grid method. Logarithmic transformation was applied to tumor volumes for the purposes of the analysis.

Highest percentage of adenocarcinoma at any biopsy site (P = 0.012), percentage of adenocarcinoma at the biopsy site with the highest Gleason score (P = 0.021), number of positive biopsy sites (P = 0.026), tumor bilaterality (P = 0.008), and percentage of biopsy sites positive for disease (P = 0.0001) all were significant predictors of tumor volume on linear regression analysis. Highest percentage of cores positive for adenocarcinoma (P = 0.081) and percentage of positive cores with carcinoma at the site with the highest Gleason score (P = 0.240) were not significant predictors of tumor volume. Based on the model F statistic, percentage of biopsy sites positive for tumor, tumor bilaterality, and highest percentage of adenocarcinoma at any biopsy site were the variables that were most predictive of tumor volume.

Highest percentage of adenocarcinoma at any biopsy site, percentage of adenocarcinoma at the biopsy site with the highest Gleason score, number of positive biopsy sites, tumor bilaterality, and percentage of biopsy sites positive for disease all are useful preoperative predictors of tumor volume in radical prostatectomy specimens. Although these preoperative biopsy parameters were significant in linear regression models, none was sufficient as a single predictor of tumor volume.