When to biopsy: How prostate MRI can transform best practice

By Philip Ward, AuntMinnie.com staff writer

December 2, 2021 -- In the era of MRI targeting, do all prostate cancer patients require an additional 12-core systematic biopsy? Moving away from default systematic biopsy in some cases may be wise, according to German researcher Dr. Dominik Deniffel, who has won a prestigious award for trainees at RSNA 2021.

Dominik Deniffel from Munich and Toronto
Dr. Dominik Deniffel from Munich and Toronto. Photo courtesy of Haider Lab.

"Shifting away from default systematic biopsy toward judiciously complementing MRI-targeted biopsy with systematic biopsy in select patients may offer the best compromise between diagnostic accuracy, the risk of biopsy complications, and overdiagnosis of clinically insignificant prostate cancer," he noted in an e-poster for which he received the Trainee Research Prize for residents.

Compared with a systematic biopsy or MRI-targeted biopsy alone, the benefit of a combined systematic and MRI-targeted biopsy is the increased detection rate of clinically significant prostate cancer. Also, the combined approach decreases the risk of upgrading at radical prostatectomy, according to Deniffel, from the Klinikum Rechts der Isar at the University Hospital of the Technical University of Munich, and colleagues at the Lunenfeld-Tanenbaum Research Institute and University Health Network (UHN) in Toronto, Canada.

On the flip side, the combined biopsy increases the number of biopsy cores and the risk of complications, and it may also increase detection of clinically insignificant (Grade Group 1) prostate cancer, they added.

The interdisciplinary team asked the following research questions:

  • How can we combine different risk factors/parameters for biopsy optimization strategies? Are there additive or synergistic effects?
  • What biopsy strategies are most clinically useful (i.e., avoidance of systemic biopsy and Grade Group 1 overdiagnosis versus missed Grade Group 2 cancers) for the entire cohort?
  • Do biopsy optimization strategies impact upgrading/downgrading at radical prostatectomy?

The researchers studied a total of 754 patients with multiparametric MRI prostate scans between July 2015 and August 2019.

The authors found that the most clinically useful strategy in patients with a low-risk threshold (less than 5%) is to perform no systematic biopsy in PI-RADS 5 cases. In those with a risk threshold greater than 5%, the best approach is to perform no systematic biopsy in men with PI-RADS 5 and/or a previous negative biopsy.

"Use of MRI-targeted biopsy alone (= omission of additional systematic biopsy) would have missed clinically significant prostate cancer in 6% of men," they stated. "The risk of missing clinically significant prostate cancer by omission of additional systematic biopsy decreased in men with PI-RADS 5 lesions, a previous negative biopsy history, and a younger age."

They conceded that this was only a retrospective single-center study, and there was no retrospective analysis of needle trajectories.

Valuable experience

Being one of the early adopters of prostate MRI in North America, both radiologists and urologists at UHN have built up extensive experience in the field over the last decade, Deniffel told AuntMinnieEurope.com.

"Translating this experience into meaningful research, however, meant a lot of groundwork, consisting of creating a comprehensive database including thousands of men undergoing prostate MRI," he said.

His research focus lies in the optimized use of information provided by prostate MRI in conjunction with clinical information to support decisions, such as referral for prostate biopsy (versus clinical follow-up) or how to avoid excessive additional systematic sampling in men undergoing MRI-targeted prostate biopsy.

"These analyses make use of a powerful analytical method which many radiologists are not yet familiar with: decision-curve analysis," Deniffel continued. "Despite the widespread adoption across different fields of medicine, it is not as commonly used in the radiology literature yet, so we hope that the practical example of our studies may help radiologists better understand the concepts and value of this analytical tool."

For the RSNA 2021 e-poster, decision curve analysis allowed the team to identify clinically useful biopsy optimization strategies, but no blanket biopsy approach works best for any clinical situation, and the best biopsy strategy depends on the decision-maker's risk tolerance for missing clinically significant prostate cancer, he explained.

Personal development

Since 2019, Deniffel has worked as a postdoctoral research fellow at the Haider Lab -- run by his mentor, Dr. Masoom A. Haider -- in the Lunenfeld-Tanenbaum Research Institute, Sinai Health System, Toronto. He was awarded a two-year postdoctoral research fellowship by the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG).

He has recently returned to Munich and now plans to finish his residency training in radiology next year. His future research will focus on strategies for the judicious use of multiparametric MRI and/or PSMA-PET imaging in different clinical scenarios, with the overarching goal of improving clinical outcomes and minimizing unnecessary diagnostic and therapeutic interventions.

"My main research interests are oncologic imaging and statistical concepts for the development and clinical implementation of risk models and artificial intelligence applications, with a focus on urogenital malignancies," he said.


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