Saturation Biopsies On Autopsied Prostates For Detecting And Characterizing Prostate Cancer

Main Category: Prostate / Prostate Cancer
Also Included In: Urology / Nephrology;  Cancer / Oncology
Article Date: 02 Nov 2008 - 0:00 PDT

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UroToday.com - This paper reports the results of a saturation biopsy protocol of 36 cores performed on 48 autopsied prostates from deceased men without any past history of prostate cancer. The first 18 cores were taken in the mid peripheral zone (6 cores), the lateral peripheral zone (6 cores) and the central zone (6 cores). An additional set of 18 cores were taken in the same locations, bringing the total number of cores to 36. Autopsied glands were then step-sectioned and analysed. We considered as "insignificant cancers" organ confined cancers with an index tumor volume <0.5 cm3 and Gleason score 6 or less.

Of the 12 cancers identified during whole mount analysis, saturation biopsies detected only 7 (58%). Moreover, all these 7 cancers were detected by the 18 first biopsy cores, meaning that doubling the number of cores did not detect any additional cancer. The 5 cancers that remained undetected by biopsies were mostly located in the mid peripheral zone and lateral peripheral zone, although one of them was unifocal and located in the central zone. However, they were missed even by doubling the number of biopsies in each of these locations. 2/5 were considered as "significant cancers": the first showed an extra-capsular extension and the other had a Gleason score of 7(3+4). These cancers were probably missed because of their low volume. Indeed, the first was unifocal with an index tumor volume of 0.42 cc, and the second was bifocal with an index tumor volume of 0.08 cc (total tumor volume of 0.16 cc).

We also found that while standard biopsies (12 first cores) underestimated Gleason score in 50% of the cases, saturation biopsies overestimated Gleason score in 43% of the cases. This tendency of saturation biopsy to overestimate pathological features has been previously reported by others [1].

Comments:

Studies evaluating prostate cancer detection are influenced by verification bias [2]. The reference standard investigation is not performed on all patients, since those with a low PSA level do not undergo prostate biopsy and those for which prostate biopsy failed to detect cancer do not undergo surgical verification. Thus, the true sensitivity of biopsy regimens is difficult to estimate. Unlike clinical studies, which fail to identify cancers present but missed by the biopsies, most cancers present in autopsied prostates can be identified and characterized. This study therefore enabled us to address a picture of saturation biopsy detection rate according to prostate cancer true prevalence.

However, our study has several limitations, the most obvious being that the definition of "clinical significance", as adopted from Stamey [3] and Epstein [4] does not include age and co-morbidities. All the cancers detected in this study would have been "clinically insignificant" since none of the deceased men were known to have prostate cancer. Nevertheless, the aim of this autopsy study was not to select best candidates for prostate cancer screening or active treatment, but only to evaluate results of saturation biopsies based on prostate cancer true prevalence and histological criteria.

References:

1. Epstein JI, Sanderson H, Carter HB, Scharfstein DO. Utility of saturation biopsy to predict insignificant cancer at radical prostatectomy. Urology 2005: 66: 356-60.
2. Punglia RS, D'Amico AV, Catalona WJ, Roehl KA, Kuntz KM. Effect of verification bias on screening for prostate cancer by measurement of prostate-specific antigen. New Engl J Med 2003: 349: 335-42.
3. Stamey TA, Freiha FS, McNeal JE, Redwine EA, Whittemore AS, Schmid HP. Localized prostate cancer. Relationship of tumor volume to clinical significance for treatment of prostate cancer. Cancer 1993: 71: 933-938.
4. Epstein JI, Walsh PC, Carmichael M, Brendler CB. Pathologic and clinical findings to predict tumor extent of nonpalpable (T1c) prostate cancer. JAMA 1994: 271: 368-74.

Written by Nicolas B. Delongchamps, Gustavo de la Roza, Richard Jones, Mary Jumbelic, and Gabriel P. Haas as part of Beyond the Abstract on UroToday.com

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