THE VOLUME OF PROSTATE-CANCER IN THE BIOPSY SPECIMEN CANNOT RELIABLY PREDICT THE QUANTITY OF CANCER IN THE RADICAL PROSTATECTOMY SPECIMEN ON AN INDIVIDUAL BASIS

Previous studies suggest that prostate cancer with a volume of 0.5 ml. or less and a Gleason score of less than 7 may be clinically insignif icant and may be managed with watchful waiting. A proposed method of d etermining the volume of cancer in the prostate gland has been the gra de and volume of cancer present in the transrectal needle biopsy speci men. Volume of cancer in the biopsy specimen as a predictor of volume of cancer in the prostate gland was studied in 130 men who underwent r adical retropubic prostatectomy for adenocarcinoma. Of the men 46 (35% ) had clinical stage T1c (nonpalpable) disease, while 84 (65%) had cli nical stage T2 (palpable) disease. Each radical prostatectomy specimen was whole-mounted and step-sectioned for accurate cancer volume deter mination. Three parameters for measuring volume of cancer in the biops y specimen (percentage of biopsy cores involved, millimeters of cancer per biopsy core and percentage of cancer in the biopsy specimen) were determined and compared by Spearman rank correlation analysis. The pe rcentage of cancer in the biopsy specimen was marginally better than t he percentage of cores involved and the millimeters of cancer per biop sy core as a predictor of cancer volume in the radical prostatectomy s pecimen. While regression analysis revealed a direct correlation betwe en the volume of cancer in the biopsy and radical prostatectomy specim ens (r = 0.51), there was significant variability in prostate cancer v olume for a given percentage of cancer in the biopsy specimen since th e standard error of the estimate was 6.1 ml. Of the 13 patients with 5 % or less cancer volume and a Gleason score of less than 7 in the biop sy specimen 1 (8%) had a cancer smaller than 0.5 ml. in volume in the radical prostatectomy specimen. Therefore, the risk of removing clinic ally insignificant prostate cancer, even when the biopsy parameter ind icates low volume disease, is less than 10%. Overall, only 3 study pat ients (2.3%) had a prostate cancer volume of less than 0.5 ml. With 97 .7% of the men having a clinically significant cancer by a volume crit erion, it is apparent that the majority of clinically insignificant pr ostate cancers remain undetected and untreated. Currently, transrectal needle biopsy does not provide adequate information for differentiati ng between clinically insignificant and life threatening prostate canc er on an individual basis.