Pre- and Postoperative DNA Ploidy Patterns Correlated to Pt-Stage, Histological Grade and Tumour Volume in Total Prostatectomy Specimens

Abstract

Fifty-four consecutive patients with a preoperative diagnosis of localized prostatic cancer underwent total retropubic prostatectomy. The specimens were step-sectioned at 5 mm intervals. Volumes of invasive cancer (IC) and prostatic intraepithelial neoplasia (PIN) were calculated by computerized planimetry. From preoperative core and fine needle aspiration biopsies and from each prostatectomy specimen, multiple samples were taken from IC and PIN areas for DNA ploidy analysis. The study aimed to evaluate current biopsy sampling techniques as regards their suitability for DNA analysis and to assess the heterogeneity of DNA-ploidy and correlate the latter to postoperative pT-stage and tumour volume. When compared with the prostatectomy specimens, the preoperative assessment of non-diploid DNA patterns in biopsies had a sensitivity of 62% and a specificity of 86%. Samples from 24 surgical specimens contained non-diploid DNA in the main tumour and in one or several of the satellites. However, all these cases also contained diploid cell lines, both in the main tumour and in one or several of the satellites. Tumours with a volume exceeding 12 cc:s were non-diploid in 87.5% of cases (7/8). Tumours with volumes between 8 and 12cc:s contained non-diploid foci in 50% of cases (2/4). Tumours smaller than 2 cc:s were non-diploid in 18% of cases (2/11). All non-diploid tumours were moderately or poorly differentiated. Of the non-diploid tumours, 96% (23/24) displayed capsular penetration versus 57% (17/30) of the diploid tumours (p < 0.0001). All PIN samples were made up of diploid cell lines. The DNA-heterogeneity of the largest tumour focus indicates that one or two preoperative biopsies may not be sufficient in order to obtain an adequate determination of the DNA pattern and systematic multi-biopsy mapping may be necessary in order to achieve this goal.

Keywords:

• prostate cancer
• DNA ploidy
• radical prostatectomy
• biopsies
• pT-stage