A blood-based risk test combining protein and genetic biomarkers with clinical data significantly reduced the number of MRI scans performed in a population prostate cancer screening program, according to results presented at the European Association of Urology Congress.
The findings come from the Stockholm3 Study in Sweden, which evaluated whether the Stockholm3 test could act as a reflex test after PSA to refine which men should proceed to MRI. The approach was designed to address a growing challenge in prostate cancer screening: while MRI improves diagnostic accuracy, large-scale screening programs could overwhelm imaging resources.
Sweden introduced organized prostate cancer testing to improve equity in screening and optimize use of diagnostic services. In the standard pathway, men with PSA levels of 3 ng/mL or higher are referred for MRI. The Stockholm3 approach adds a second step: men with PSA of at least 2 ng/mL undergo the Stockholm3 blood test, and MRI is recommended only if the algorithm score is at least 15.
The population-based trial compared two cohorts invited for screening in consecutive years. In the control group following the PSA-only pathway, 6,822 men underwent PSA testing and 2.8 percent had PSA levels of at least 3 ng/mL. In the experimental cohort, 7,079 men underwent PSA testing, of whom 627 (8.9 percent) received Stockholm3 testing.
The addition of Stockholm3 had a substantial impact on downstream imaging. MRI use fell from 2.7 percent of screened men to 1.1 percent, representing a 60 percent relative reduction. Biopsy rates also declined, dropping from 0.6 percent to 0.4 percent.
Cancer detection rates were similar but numerically lower in the experimental pathway. Low-grade (Grade Group 1) prostate cancer was detected in eight men in the control group and six men in the Stockholm3 group. Clinically significant cancers (Grade Group ≥2) were detected in 15 men and eight men, respectively, although the estimates carried wide confidence intervals.
Investigators also evaluated a stricter reflex-testing strategy in which Stockholm3 was used only for men with PSA levels of at least 3 ng/mL. This approach further reduced testing demand – cutting Stockholm3 use by 63 percent and MRI scans by 67 percent – while maintaining detection of clinically significant cancers.
The results highlight the potential of multi-marker blood tests combined with algorithmic risk assessment to triage imaging resources. By filtering which patients proceed to MRI and biopsy, such strategies may help make population prostate cancer screening more scalable while limiting unnecessary procedures and reducing the demand on imaging services.
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