MRI Plus New Score Halves Biopsy Rate for Prostate Cancer

Neil Osterweil

July 09, 2021

More good tidings to gladden the hearts of men who have reached the half century mark: Swapping traditional prostate biopsies for MRI-targeted biopsies with a new prostate cancer risk score can cut the number of unnecessary biopsies in half while still detecting clinically significant cancers.

The findings from the STHLM3MRI study, a large randomized trial, were published online in The New England Journal of Medicine to coincide with a presentation of the results at European Association of Urology 2021 Annual Meeting (EAU 2021).

The trial included nearly 2300 men with elevated prostate-specific antigen (PSA) levels and/or high scores on the Stockholm 3 predictive test.

They were randomly assigned to undergo either systematic biopsy or Stockholm 3 testing plus MRI with biopsy only of suspicious lesions.

The results show that the MRI-targeted strategy was associated with a 52% reduction in biopsy procedures compared with the systematic approach and a 69% reduction in detection of low-grade (Gleason score 6) cancers, reported Tobias Nordström, MD, PhD, from the Karolinska Institute, in Stockholm, Sweden.

"Combining the Stockholm 3 test with an MRI-targeted biopsy approach for prostate cancer screening decreases overdetection while maintaining detection of significant prostate cancer," he said at the meeting.

"It is exciting to see breakthroughs such as this in the field of early detection of prostate cancer. An innovation such as STHLM3MRI makes an even more compelling case for the European Commission to ensure a risk-stratified approach to early detection of prostate cancer is adopted across the whole of Europe," commented Hendrik Van Poppel, MD, PhD, adjunct secretary general of the EAU.

Although routine screening for breast and colorectal cancer is widely performed in Europe, to date, only Lithuania has established a nationwide program for prostate cancer screening, according to the EAU.

The Stockholm 3 test, developed at the Karolinska Institute, includes clinical variables (age and previous biopsy status) and a single-nucleotide-based genetic score, as well as measurements of five protein levels: total PSA, free PSA, human kallikrein 2, microseminoprotein-beta, and macrophage inhibitory cytokine 1.

MRI-Guided Biopsy Studies

Several recent major clinical trials have highlighted the advantages and potential drawbacks of MRI-targeted biopsy compared with transrectal ultrasound–guided 12-core systematic biopsy.

As previously reported by Medscape Medical News, the European PRECISION trial and its Canadian sister, the PRECISE trial, showed that an MRI-guided technique identified more clinically significant cancers and reduced the need for biopsy.

The new wrinkle introduced in STHLM3MRI trial is the addition of the Stockholm 3 score, which was added in an attempt to improve accuracy and reduce identification of clinically unimportant low-grade tumors.

The investigators invited 49,118 men aged 50 to 74 years to be screened; of these patients, 12,750 agreed. These men gave blood samples that were tested for PSA and Stockholm 3 parameters.

Men with PSA levels of ≥3 ng/mL and/or Stockholm 3 scores of ≥0.11 (n = 2293) were then randomly assigned to undergo either standard biopsy or an MRI-targeted strategy in which biopsy was performed on men with Prostate Imaging Reporting and Data System scores of ≥3.

Most MRI scans were performed on 1.5 Tesla machines. The scans were performed without contrast using a fast protocol. The acquisition time was approximately 12 min.

The median age of the participants was 61 years, and the mean PSA level was 1.0 ng/mL.

The investigators found that the area under the curve of receiver operating characteristics for detection of significant cancers, defined as a Gleason score of ≥7, was 0.76 for the Stockholm 3 test and 0.60 for PSA.

Using data from 1372 men enrolled in the experimental (MRI) arm of the study, the team observed that a Stockholm 3 score cutoff of 0.15 or higher was comparable to a PSA level of ≥3 ng/mL in sensitivity for detecting significant cancers.

The Stockholm 3 test decreased the need for MRI by 36% and the number of biopsy procedures by 8%, although the latter difference was not statistically significant.

Comparing the PSA plus systematic biopsy arm with Stockholm 3 plus MRI-targeted biopsy in the entire randomized population, they found that the MRI strategy was associated with a halving of the biopsy rate.

"We conclude that the Stockholm 3 test can inform risk stratification before MRI and targeted biopsies in prostate cancer screening," Nordström said.

The research was financed by the Swedish Cancer Society, the Swedish Research Council, the Swedish Research Council for Health, Working Life and Welfare, the Karolinska Institutet, Hagstrandska Minnesfonden, Region Stockholm, the Swedish Order of Druids, the Åke Wiberg Foundation, the Swedish e-Science Research Center (SeRC), and Prostatacancerförbundet (the Prostate Cancer Association). Nordström and two co-authors are partners of the company A3P Biomedical AB, which holds the development rights of the Stockholm 3 test. Van Poppel has disclosed no relevant financial relationships.

N Engl J Med. Published online July 9, 2021. Abstract

European Association of Urology 2021 Annual Meeting (EAU 2021): Abstract P1014.

Neil Osterweil, an award-winning freelance medical journalist, is a long-standing and frequent contributor to Medscape.

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