Point: Is MRI fusion biopsy the new gold standard for diagnosis?

Advances in magnetic resonance imaging (MRI) technology have led to increased utilization of MRI for prostate cancer evaluation, and results from studies evaluating the performance of MRI fusion biopsy provide clear evidence to support its use as the gold standard for men at risk for prostate cancer diagnosis following an initial negative biopsy, according to Michael S. Cookson, MD, and Kelly L. Stratton, MD. 

“In its most recent policy statement relating to MRI use in prostate cancer, the AUA supports fusion biopsy for men with a prior negative biopsy. And for biopsy-naïve men, it suggests that fusion biopsy may benefit those with uncertain clinical indications for biopsy, such as minimal PSA increase, abnormal digital rectal exam with normal PSA, or marginal indications based on age.¹ The current NCCN Guidelines for Prostate Cancer Early Detection state that for initial and repeat transrectal ultrasound (TRUS)-guided biopsy, multiparametric MRI (mpMRI) followed by lesion targeting may maximize the detection of higher risk disease and limit the detection of lower risk disease,²” said Dr. Cookson, professor and chairman of the department of urology, University of Oklahoma College of Medicine, Oklahoma City.

Related - Counterpoint: Is MRI fusion biopsy the new gold standard for diagnosis?

“Although the NCCN guidelines also note that MRI is not recommended routinely prior to initial prostate biopsy, we believe that studies supporting the utility of prostate MRI will create the basis for its earlier use.”

Dr. Stratton, assistant professor of urology at the University of Oklahoma, said, “There is little debate that repeat biopsy following a prior negative biopsy is improved by using prostate MRI technology, and in the interest of controlling cost, some may argue that MRI fusion biopsy should be limited to this population. It makes more sense, however, to obtain the MRI when the prostate cancer diagnosis is first suspected, prior to any decision for biopsy.

“The fact that many men initially have a negative biopsy means that repeat biopsy is an inevitability for any urologist,” Dr. Stratton added. “Clinicians will have to determine how they want to handle that situation. As more and more urologists become familiar with the technology, the use of prostate MRI and fusion biopsy will continue to grow. Its benefits for improving cancer detection, clarifying anatomical detail, and potentially assisting in staging cancer spread make prostate MRI and fusion biopsy the new gold standard for prostate biopsy.”

Next: Benefits of MRI fusion biopsy

Benefits of MRI fusion biopsy

mpMRI is the cornerstone of fusion biopsy. Because this technology utilizes several image series to obtain both anatomical assessments of the prostate and physiologic assessments that represent potential changes arising from tumor cell proliferation, it not only helps identify prostate cancer but also directs the biopsy to areas of clinically significant disease, said Dr. Stratton.

Also see - Point: Is HIFU for low-risk prostate Ca ready for prime time?

Many reports show that mpMRI fusion biopsy improves biopsy accuracy. For example, in a retrospective study of 135 patients undergoing prostatectomy, Baco et al reported that the index lesion identified on mpMRI fusion biopsy was concordant with findings from prostatectomy pathology in 95% of patients.³

Other research shows the benefits of mpMRI fusion biopsy for maximizing detection of higher risk disease and limiting detection of low-risk disease. For example, in the multicenter PROMIS study that included 576 biopsy-naïve men, patients underwent mpMRI followed by mapping biopsy and TRUS biopsy.⁴ The study found that including mpMRI would improve the detection of clinically significant prostate cancer by 18% while potentially reducing the detection of clinically insignificant cancer by 5%.

Radtke et al studied 294 consecutive biopsy-naïve men undergoing combined transperineal template saturation biopsy and MRI-guided targeted biopsy, including 186 men who were biopsy-naïve and 108 men who had a prior negative biopsy.⁵ Targeted biopsy of PI-RADS 2-5 lesions missed fewer clinically significant (Gleason score ≥7) cancers than the systematic biopsy (11 [12.8%] vs. 18 [20.9%]) and also missed 43.8% of Gleason score 6 tumors. If the targeted biopsy was limited to PI-RADS 3–5 lesions, it would have missed 17 significant cancers (19.8%).

“These results show that while targeted fusion biopsy can reduce detection of lower grade disease, the gold standard to optimize diagnosis of clinically significant prostate cancer should be combined systematic and targeted fusion biopsy,” said Dr. Stratton.

Similarly, results of a study by Tran et al evaluating the utility of MRI fusion biopsy in men undergoing a confirmatory biopsy as part of an active surveillance regimen support its use for guiding clinical decisions, but also indicate that in this setting as well, MRI fusion biopsy is best used in combination with systematic biopsy and not as a replacement for it.⁶ Among 207 men undergoing MRI fusion biopsy with concurrent systematic biopsy, 83 men (40%) were upgraded after biopsy, but the upgrading was based on systematic biopsy alone in 49 men, MRI fusion biopsy alone in 30 men, and both techniques in four men.

Addressing the idea that MRI fusion biopsy should not be considered the gold standard for prostate cancer diagnosis because it is inferior to mapping biopsy, Dr. Cookson and Dr. Stratton did not dispute the fact that mapping biopsy would provide an accurate representation of any pathology present in the prostate.

Read - Counterpoint: Is HIFU for low-risk prostate Ca ready for prime time?

“Just as with MRI fusion biopsy, however, there are concerns with cost and utilization of resources accompanying the use of mapping biopsies,” Dr. Cookson said.

Next: Ensuring quality

Ensuring quality

Although published studies support the adoption of MRI fusion biopsy for prostate cancer diagnosis, its value, as noted in a 2016 joint consensus statement from the AUA and the Society for Abdominal Radiology, depends on high-quality prostate MRI and experienced radiologic interpretation.⁷

“Urologists considering building a fusion biopsy program should work with their radiology colleagues to evaluate the technology that is locally available and should team up with a radiology champion, reviewing cases together and confirming histological diagnosis to quickly build expertise and ensure quality interpretation,” Dr. Stratton said.

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References

1.  Fulgham PF, Rukstalis DB, Turkbey IB, et al. AUA Policy Statement on the Use of Multiparametric Magnetic Resonance Imaging in the Diagnosis, Staging and Management of Prostate Cancer. J Urol 2017; 198:832-8.

2.  Carroll PR, Parsons JK, Andriole G, et al. NCCN Guidelines Insights: Prostate cancer early detection, version 2.2016. J Natl Compr Canc Netw 2016; 14:509-19.

3.  Baco E, Ukimura O, Rud E, et al. Magnetic resonance imaging-transectal ultrasound image-fusion biopsies accurately characterize the index tumor: correlation with step-sectioned radical prostatectomy specimens in 135 patients. Eur Urol 2015; 67:787-94.

4.  Ahmed HU, El-Shater Bosaily A, Brown LC, et al. Diagnostic accuracy of multi-parametric MRI and TRUS biopsy in prostate cancer (PROMIS): a paired validating confirmatory study. Lancet 2017; 389:815–22.

5.  Radtke JP, Kuru TH, Boxler S, et al. Comparative analysis of transperineal template saturation prostate biopsy versus magnetic resonance imaging targeted biopsy with magnetic resonance imaging-ultrasound fusion guidance. J Urol 2015; 193:87–94.

6.  Tran GN, Leapman MS, Nguyen HG, et al. Magnetic resonance imaging-ultrasound fusion biopsy during prostate cancer active surveillance. Eur Urol 2017; 72:275–81.

7.  Rosenkrantz AB, Verma S, Choyke P, et al. Prostate magnetic resonance imaging and magnetic resonance imaging targeted biopsy in patients with a prior negative biopsy: a consensus statement by AUA and SAR. J Urol 2016; 196:1613–8.

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