Standardized in vitro mapping with multiple core biopsies of total prostatectomy specimens: localization and prediction of tumour volume and grade

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Abstract
To analyse the ability of systematic core biopsy mapping to provide prognostic information in patients with prostatic cancer. The prostates of 60 men with prostatic cancer, stages T0d-T2, who had undergone total retropubic prostatectomy were studied. The average age of the patients was 63 years (range 49-72). Ten core biopsies (1.2 x 35 mm) were taken from the fresh specimens according to a standardized procedure. The total prostatectomy specimens were serially step-sectioned at 5 mm intervals and were assessed regarding tumour volume, grade and pT-stage. The World Health Organization (WHO) grade obtained in the mapping biopsies was compared with that in the operative specimens. Undergrading (WHO) decreased substantially by mapping biopsies, but was still present with the Gleason system. The volume of extracapsular tumours with extensively positive margins was significantly larger than that of intracapsular tumours (P < 0.01). In addition, the fraction of cancer obtained in the biopsies from tumours with grossly positive margins was significantly smaller than that observed in biopsies from pT2 tumours (P < 0.01). The cancer volume calculated from the result of the mapping correlated positively with the tumour volume determined by planimetry (R = 0.83). A weaker correlation was found when only the six dorsal mapping biopsies were taken into consideration (R = 0.68), but the correlation increased to R = 0.75 when the six most significant biopsies were selected with the help of a correlation matrix. Biopsies from the ventral part of the prostate were also important, to obtain an accurate assessment of the tumour fraction within the whole gland. Mapping of the prostate gland with multiple (six or more) core biopsies is necessary for preoperative assessment of tumour volume, grade and pT stage; these are all of importance when assigning patients with clinically localized prostatic cancer to prognostic classes.