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MRI-targeted prostate biopsy: The future of cancer diagnosis? "Beyond the Abstract," by Fergus V. Coakley, MD

BERKELEY, CA (UroToday.com) - In our recently published study,[1] we retrospectively reviewed our preliminary experience following the introduction of an MRI-guided prostate biopsy program at UCSF. Our findings are encouraging; MRI-guided biopsy was positive in 5 of 7 patients with suspected prostate cancer (including 2 of 4 with prior negative ultrasound-guided biopsies) and in 8 of 12 with known, untreated prostate cancer (including 5 where MRI-guided biopsy demonstrated a higher Gleason score than ultrasound guided biopsy results). These results are aligned with other larger similar studies,[2, 3, 4] which have consistently indicated that targeted biopsy yields information on prostate cancer presence and aggressiveness that is equivalent or superior to standard transrectal ultrasound-guided systematic biopsy. While transrectal ultrasound-guided systematic biopsy is the current “gold standard” for prostate cancer diagnosis, it is instructive to compare the diagnostic approach to breast cancer, another common primary malignancy. For breast cancer, a tumor is usually first identified on mammography and only that target is biopsied. It is inconceivable that breast cancer would be diagnosed by placing twelve needles at standard locations in the breast, yet this is effectively the current “state-of-the-art” for prostate cancer diagnosis. Approximately 60% of men with a suspicious PSA or digital rectal examination have a visible disease site at multiparametric prostate MRI.[5] In this population, there is arguably a logical rationale to only biopsy the visible target. The counter-argument that systematic biopsy is required because prostate cancer is multifocal is debatable, given new understandings on the limited biological importance of multifocality:

  • Non-index tumors are usually small - about 80% of non-index tumors are less than 0.5 cm3[6] and, on average, secondary foci only constitute 12% of total cancer volume.[7]
  • Non-index tumors are usually of lower or equivalent stage and grade - in 100 prostatectomy specimens, none of the 170 secondary foci had a higher Gleason score than the index lesion and 169 had a Gleason score of 6 or less.[8] Only 2 non-index foci extended beyond the capsule, but in one of these cases, the index tumor also had extracapsular extension. No secondary foci invaded the seminal vesicles.
  • Non-index tumors do not seem to drive outcome - repeated and independent studies have shown that non-index tumor characteristics are unrelated to patient outcome.[7, 9, 10] In parallel with these empirical observations, advances in basic research have led to increasing emphasis on the biological importance of the index lesion.[11]

Such an MRI-targeted approach would represent a major shift away from the current diagnostic method, but might help reduce the current, relatively high rate of false negative and undergrading results by systematic biopsy. Despite the emerging data, we suspect it is unlikely that urologists in North American will move away from standard systematic biopsy until a “head to head” comparative study using robust and generalizable techniques is performed at established academic medical centers and demonstrates that targeted MRI-guided biopsy is equivalent or superior to systematic biopsy with respect to cancer diagnosis and characterization. We eagerly await the performance of such a trial.

References:

  1. Jung AJ, Westphalen AC, Kurhanewicz J, Wang ZJ, Carroll PR, Simko JP, Coakley FV. Clinical utility of endorectal MRI-guided prostate biopsy: Preliminary experience. J Magn Reson Imaging. 2014 Aug;40(2):314-23.
  2. Siddiqui MM, Rais-Bahrami S, Truong H, Stamatakis L, Vourganti S, Nix J, Hoang AN, Walton-Diaz A, Shuch B, Weintraub M, Kruecker J, Amalou H, Turkbey B, Merino MJ, Choyke PL, Wood BJ, Pinto PA. Magnetic resonance imaging/ultrasound-fusion biopsy significantly upgrades prostate cancer versus systematic 12-core transrectal ultrasound biopsy. Eur Urol. 2013 Nov;64(5):713-9.
  3. Pokorny MR, de Rooij M, Duncan E, Schröder FH, Parkinson R, Barentsz JO, Thompson LC. Prospective study of diagnostic accuracy comparing prostate cancer detection by transrectal ultrasound-guided biopsy versus magnetic resonance (MR) imaging with subsequent MR-guided biopsy in men without previous prostate biopsies. Eur Urol. 2014 Jul;66(1):22-9.
  4. Da Rosa MR, Milot L, Sugar L, Vesprini D, Chung H, Loblaw A, Pond GR, Klotz L, Haider MA. A prospective comparison of MRI-US fused targeted biopsy versus systemic ultrasound-guided biopsy for detecting clinically significant prostate cancer in patients on active surveillance. J Magn Reson Imaging. 2014 Jul 21. doi: 10.1002/jmri.24710. [Epub ahead of print]
  5. Moore CM, Robertson NL, Arsanious N, Middleton T, Villers A, Klotz L, Taneja SS, Emberton M. Image-guided prostate biopsy using magnetic resonance imaging-derived targets: A systematic review. Eur Urol 2013; 63: 125-40.
  6. Meiers I, Waters DJ, Bostwick DG. Preoperative prediction of multifocal prostate cancer and application of focal therapy: Review 2007. Urology 2007; 70 (Suppl 6A): 3–8.
  7. Stamey TA, McNeal JM, Wise AM, Clayton JL. Secondary cancers in the prostate do not determine PSA biochemical failure in untreated men undergoing radical retropubic prostatectomy. Eur Urol 2001;39 (Suppl 4): 22-23.
  8. Karavitakis M, Winkler M, Abel P, Livni N, Beckley I, Ahmed HU. Histological characteristics of the index lesion in whole-mount radical prostatectomy specimens: Implications for focal therapy. Prostate Cancer and Prostatic Diseases 2011; 14: 46-52.
  9. Muezzinoglu B, Frolov A, Ohori M, et al. Clinicopathologic significance of multifocal prostate cancer. Lab Invest 2006; 86: 151A.
  10. Noguchi M, Stamey TA, McNeal JE, Nolley R. Prognostic factors for multifocal prostate cancer in radical prostatectomy specimens: lack of significance of secondary cancers. J Urol 2003; 170: 459–63.
  11. Ahmed HU. The index lesion and the origin of prostate cancer. NEJM 2009; 361: 1704-1706.

Written by:
Fergus V. Coakley, MD 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.

Departments of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California USA

Clinical utility of endorectal MRI-guided prostate biopsy: Preliminary experience - Abstract

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