BERKELEY, CA (UroToday.com) - Routine biopsy of the prostate transition zone (TZ) is not recommended as yield of cancer detection is known to be low. However, for patients already diagnosed with cancer and managed with active surveillance (AS), the intent of biopsy is different. The onus is on the clinician to consider unsampled regions, such as the TZ, which could potentially harbor more aggressive cancer.
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At our institution, TZ biopsies have routinely been taken at re-biopsy for men on AS. A total of 2-4 TZ cores are taken from the thickest part of the prostate in the immediate paraurethral region.
Our results showed that cancer in the TZ was found in 18.6-26.7% of men at each biopsy with more significant disease (defined as Gleason sum ≥ 7 and/or > 50% single core involved) found in 5.9-11.1%. More importantly, 2.7-6.7% of men had significant disease found only in the TZ biopsies and represent the group where disease “progression” would have been missed if TZ biopsies had not been performed. These proportions were remarkably consistent at each re-biopsy time point for our men on AS.
When compared to transperineal template mapping biopsies of the prostate, the incidence of TZ cancer we described (18.6-26.3% versus 24.1%) was similar but with fewer TZ cores (2-4 versus 11). Both transperineal biopsy technique and multi-parametric MRI of the prostate allow better examination of the anterior prostate, among other benefits. Undoubtedly, their roles in AS for prostate cancer will continue to develop as experience and accessibility increase. Currently repeated transrectal ultrasound-guided prostate biopsy remains the most commonly practiced method of monitoring men on AS. Thus, our findings represent a potential immediate change that could impact men on AS.
The significance of our results is likely to be debated. Skeptics will likely point out that most of the more “aggressive disease” found was increased volume of cancer (> 50% single core, n=22/31) rather than increased Gleason grade (n=9/31). The significance of higher volume of Gleason 3+3 disease found at biopsy remains to be determined but it may suggest increased risk of upgrading. The opinion of our institution is that taking an extra 2-4 TZ cores at prostate biopsy is unlikely to add morbidity and is of potential benefit in diagnosing more significant disease for approximately 1-in-20 men.
- Pelzer, A.E. et al., 2005. Are Transition Zone Biopsies Still Necessary to Improve Prostate Cancer Detection? Results from theTyrol Screening Project. Eur Urol, 48, pp.916–921.
- Patel, V. et al., 2011. The Incidence of Transition Zone Prostate Cancer Diagnosed by Transperineal Template-guided Mapping Biopsy: Implications for Treatment Planning. Urology, 77(5), pp.1148–1152.
Lih-Ming Wong as part of Beyond the Abstract on UroToday.com. This initiative offers a method of publishing for the professional urology community. Authors are given an opportunity to expand on the circumstances, limitations etc... of their research by referencing the published abstract.
Division of Surgical Oncology, Department of Uro-oncology, Princess Margaret Cancer Center, University Health Network, Department of Radiology, Princess Margaret Hospital, Department of Pathology, Toronto General Hospital and Department of Medicine, University of Toronto, Toronto, Ontario, Canada, and Department of Urology, St. Vincent's Hospital and Austin Health, University of Melbourne, Victoria, Australia