A prostate cancer screening strategy using MRI with targeted and standard biopsy reduced the detection of clinically insignificant cancers as well as unnecessary biopsies, researchers reported.

Such an approach was also as effective as a standard biopsy strategy in detecting clinically significant cancers, said Tobias Nordstrom, MD, PhD, of the Karolinska Institutet in Stockholm, in a presentation at the virtual European Association of Urology Congress.

The results were published simultaneously in the New England Journal of Medicine (NEJM).

Nordstrom and colleagues found that the detection of clinically insignificant tumors and benign findings on biopsy were lower by 64% and 74%, respectively, among men with elevated prostate-specific antigen (PSA) levels, when biopsy was performed when MRI results were positive rather than using a standard strategy.

“Overdiagnosis is a critical barrier to any screening implementation of prostate cancer,” Nordstrom said. “We all know from studies performed before that MRI with targeted biopsies reduces overdiagnosis in men referred to prostate biopsy in clinical cohorts. But there is a lack of evidence on how MRI performs in a screening population.”

The prospective, randomized, population-based STHLM3-MRI trial included men ages 50 to 74 and was designed to evaluate different screening strategies for prostate cancer. In this analysis, Nordstrom reported findings from a strategy that combined MRI-targeted and standard biopsy in men with positive results on MRI compared with use of a standard biopsy strategy.

The study included 12,750 men, 1,532 of whom had a PSA level of ≥3 ng/mL. Of these, 603 were randomized to undergo standard biopsy, and 929 to MRI, with targeted and standard biopsy if the MRI results indicated prostate cancer.

The primary outcome was the probability of detection of clinically significant prostate cancer (the percentage of patients with a Gleason score of 3+4 or greater). Key secondary outcomes included the detection of clinically insignificant cancers and biopsies with benign findings.

“We found that the MRI-targeted strategy was non-inferior for the detection of significant cancers,” Nordstrom reported. “However, we could not deem the MRI-targeted strategy as superior.”

The team did find, however, that the MRI-targeted strategy detected fewer clinically insignificant cancers (Gleason score 6). Specifically, 4% of the cancers detected with MRI-targeted biopsy were Gleason score 6 compared with 12% in the standard-biopsy arm, for a difference of -8% (95% CI -11% to -5%).

When Nordstrom and co-authors normalized the findings to 10,000 men (ages 50 to 74 with elevated PSA levels of 3 ng/mL or more) the targeted biopsy approach in men with a positive MRI resulted in:

• 409 fewer men undergoing biopsy

• 366 fewer biopsies with benign findings

• 88 fewer clinically insignificant cancers

Those numbers represented 48%, 78%, and 62% lower incidences, respectively, with the use of MRI and the combined biopsy approach, Nordstrom reported.

In the NEJM article, the researchers explained that an important question was whether men with positive MRI results should undergo a standard biopsy in addition to targeted biopsy. The findings showed that the addition of standard biopsy resulted in the discovery of 30 more clinically significant cancers among the men in the experimental biopsy group and the detection of 18 fewer insignificant cancers.

“Thus, detection of 1.7 clinically significant cancers would be delayed for each clinically insignificant cancer avoided,” the investigators calculated. “Our results therefore support the use of standard biopsy in addition to targeted biopsy for men who have positive MRI results, an observation that is in line with previous findings.”

In addition, the team said, a reduced biopsy rate and potential downstream savings from reducing overtreatment could result in costs savings that would offset the additional costs of MRI.