By: Dan Sperling, MD

In a side-by-side comparison study, a collaborative team of researchers from The Netherlands and Australia found that MRI-guided targeted prostate biopsy was more accurate than standard TRUS (transrectal ultrasound) guided biopsy. Pokorny et al. (2014) reported their research findings at the 29^th annual European Association of Urology conference and in 2015 published their results in the authoritative journal European Urology.[i] The conference presentation to mostly urologists catalyzed considerable discussion, while the published article sparked a published response from Shanmugabavan et al[ii] and a rejoinder by the original authors.[iii]

The context for the study was the problem of sampling errors that can occur with systematic TRUS biopsy, which is essentially random and blind since ultrasound does not reveal tissue changes that are characteristic of prostate cancer (PCa). The investigators identified three problems that can occur because of TRUS biopsy sampling error: delayed diagnosis, overdetecting indolent PCa, and misclassification. They hypothesized that multiparametric MRI, which is highly sensitive to significant PCa, would identify which men needed a biopsy and which could safely avoid a biopsy and continue to be monitored. Their research was designed as a prospective, investigator-blinded study that was conducted from July 2012-January 2013. The team enrolled 223 men suspected of having prostate cancer (PCa) based on elevated PSA who had not yet undergone a biopsy.

All study participants had multiparametric MRI (mpMRI) prostate scans. Those whose MRIs revealed suspicious areas (142 patients) then underwent in-bore MRI-guided targeted biopsy. All patients had TRUS biopsy regardless of the MRI results. Of the 223 men, a total of 142 (63.7%) were diagnosed with PCa.

The table below gives a breakdown of key data:

According to the team’s computations, the MRI targeted biopsy as a diagnostic pathway “reduced the need for biopsy by 51%, decreased the diagnosis of low-risk PCa by 89.4%, and increased the detection of intermediate/high-risk PCa by 17.7%.” They concluded that MRI-guided targeted biopsy offers a superior method of detecting and diagnosing PCa.

In an interview following presentation of the paper at the European conference, lead investigator Dr. Morgan Pokorny commented, “I think the future lies with MRI… We’re not categorically saying you shouldn’t do TRUS­ guided biopsies, but we think that MRI can help you risk­ stratify very powerfully — more so than any other tool.”[iv] He pointed out the need for urologists and radiologists to work together in the best interests of patients. Some of the urologists at the conference pointed out that when TRUS is done well, diagnostic rates exceed 50%, but perhaps the real issue is the significance of the tumor at diagnosis. Dr. Pokorny pointed out, “Overall, our study showed that you find more significant cancers with MRI than with TRUS­guided biopsy… The 2 together will give you the best outcome, but I think as a society and as professionals, we should move toward a goal of trying to do less on men than we’re currently doing. In other words, biopsy fewer men and put fewer needles into prostates.” At the same time, spokespersons for urology noted that in-bore MRI-guided biopsies are not commonly available or even affordable. The technology for fusion guidance, which co-registers (merges point by point) MRI images with real-time ultrasound is one way of bringing MRI results into the urology practice. Perhaps most important, larger randomized studies with standardized criteria for insignificant vs. significant PCa are needed to determine whether MRI-targeted in-bore biopsies are significantly more accurate to justify the extra cost.

There is no doubt that prostate cancer detection and diagnosis are evolving toward greater use of multiparametric MRI for detection and more precise targeting of tumors for diagnosis. The work of Pokorny and others will continue to drive research and development for improving the prostate biopsy experience.

[i] Pokorny MR, de Rooij M, Duncan E, Schröder FH et al. Prospective study of diagnostic accuracy comparing prostate cancer detection by transrectal ultrasound-guided biopsy versus magnetic resonance (MR) imaging with subsequent MRI-guided biopsy in men without previous prostate biopsies. Eur Urol. 2014 Jul;66(1):22-9.

[ii] Shanmugabavan Y, Guillaumier S, Ahmed HU. Re: Morgan R. Pokorny, Maarten de Rooij, Earl Duncan, et al. Prospective study of diagnostic accuracy comparing prostate cancer detection by transrectal ultrasound-guided biopsy versus magnetic resonance (MR) imaging with subsequent MRI-guided biopsy in men without previous prostate biopsies. Eur Urol 2014;66:22-9. In Eur Urol. 2015 Mar;67(3):e52-3.

[iii] Pokorny M, Van de Ven W, Barentsz J, Thompson L. Reply to Yaalini Shanmugabavan, Stephanie Guillaumier and Hashim U. Ahmed’s letter to the editor re: Morgan R. Pokorny, Maarten de Rooij, Earl Duncan, et al. Prospective study of diagnostic accuracy comparing prostate cancer detection by transrectal ultrasound-guided biopsy versus magnetic resonance (MR) imaging with subsequent MRI-guided biopsy in men without previous prostate biopsies. Eur Urol 2014;66:22-9. In Eur Urol. 2015 Mar;67(3):e54-5.

[iv] Reported for Medscape by Kate Johnson, April 18, 2014. http://www.medscape.com/viewarticle/823847