Heterogeneity and biopsy strategies in prostate cancer
Abstract: For the diagnosis of prostate cancer, there is a need to develop biopsy strategies, that give representative information both for detection of cancer and for assessment of prognostic indicators.In 80 men, transrectal core biopsies from 10 standardized positions were taken before radical prostatectomy. The total cancer length of the biopsies significantly correlated with the tumor volume as measured in the operation specimens. Focal, low - moderate grade cancer in a single biopsy had a positive predictive value of 90% for tumor volume less than 1 ml.A new technique was developed for handling prostatectomy specimens allowing sampling of fresh tissue and providing landmarks for alignment of whole-mount sections.Testing of biopsy protocols is limited by pain and risk of side effects. A computerized 3D model of prostate cancer was developed for biopsy simulations and conclusions from the preoperative biopsies were confirmed.The model was also used to estimate the stability of biopsy protocols. In total, 32 400 biopsies were generated by moving the standardized biopsies. The effects on the diagnostic yield by 1 - 4 mm parallel translations or 5 - 20 degree rotations were calculated. A changed insertion point had greater impact on the cancer yield than a changed needle angle.The DNA ploidy was assessed in 51 prostates (average 14.7 samples per case). Ploidy heterogeneity was found in 42% of the cases and 58% were diploid. The volume of non-diploid cancer was estimated and was found to correlate with local tumor stage.
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