Impact of multiple biopsy cores on predicting final tumor volume in prostate cancer detected by a single microscopic focus of cancer on biopsy

Objectives. To compare the impact that the number of biopsy cores have on final pathologic findings when minimal disease is detected at biopsy. Discordance has been noted between transrectal ultrasound-guided biopsy results and tumor volume even when minimal amounts of tumor are found on biopsy. Methods. We identified patients who had undergone radical retropubic prostatectomy for a single microscopic focus of adenocarcinoma from a prospectively maintained surgical database. Patients were stratified into two groups: those with six biopsies or less and those with seven or more. The Gleason score, margin status, presence of extracapsular extension, and percentage of tumor volume were compared. Results. A total of 102 patients in our database had a single microscopic focus of adenocarcinoma detected by needle biopsy. Of these patients, 65 underwent six or fewer biopsies and 37 underwent seven or more at transrectal ultrasonography. Of the 37 patients in group 2, 27 (73%) had a final tumor volume of less than 5% compared with 24 (37%) of 65 patients in group 1 (P = 0.002). Of the group 2 patients, 15 (75%) with Stage T1c had an estimated tumor volume of less than 5% compared with only 11 (34%) in group 1 (P = 0.01). No statistically significant difference was noted between the two groups for margin status, presence of extracapsular extension, or Gleason score. Conclusions. A single microscopic focus of cancer obtained after multiple cores predicts for a significantly lower tumor volume on final pathologic examination across clinical stages. In the context of greater tissue sampling, the minimal disease designation may carry more predictive value and be a useful parameter in stratifying patients with Stage T1c and other good-risk factors with regard to surgical outcome.