Detailed mapping of prostate carcinoma foci: biopsy strategy implications

Abstract

Background: Prostate carcinoma exhibits considerable anatomic heterogeneity. Detailed characterization of prostate carcinoma distribution could lead to improved detection procedures and biopsy strategies. We mapped all 607 tumor foci from 180 serially sectioned whole mount radical prostatectomy specimens and used a computer algorithm to plot and summarize the distribution of these foci. We investigated whether specimen and clinical variables predicted differences in tumor distribution.

Methods: The volume and anatomic location of each tumor focus were determined and digitized. A computer-based algorithm was used to fit the digitized tumor foci to a paradigm prostate. Pseudo-color summary plots of tumor distribution then were computed for selected cases.

Results: Of the 180 specimens, 149 (83%) specimens had more than one cancer focus. Most foci (448 of 607 tumor foci, 74%) were in the peripheral zone (PZ). PZ foci near the apex had a significant midline component. Toward the base, PZ foci diverged laterally. Only 3 (2%) of 180 specimens contained foci solely in the transition zone (TZ). Total TZ cancer volume was </= 0.5 cm(3) in 55% (52 of 94) of patients. Computer plots of patients with T1c classification (UICC/AJCC) and specimen Gleason score </= 6 had greater proportions of TZ tumor.

Conclusions: Almost all TZ foci occurred with PZ foci. The small volume of most TZ foci may explain the ineffectiveness of TZ biopsies to detect additional cancers during screening. Further, our results suggested that biopsies may be more effective if laterally directed biopsy samples are obtained nearer to the base of the prostate and if apical biopsy samples are obtained more medially.