Full Breakdown
Stockholm3 Blood Test Outperforms PSA in Detecting Aggressive Prostate Cancer
6/28/2026, 11:02:29 AM
Study Findings and Core Results
A prospective clinical trial published in the *Annals of Internal Medicine* evaluated the Stockholm3 blood test against the standard prostate-specific antigen (PSA) assay. More than 12,000 men aged 50-74, primarily from Sweden and other European countries, received both tests and were followed for two years. During follow-up, 443 participants were diagnosed with aggressive prostate cancer. Stockholm3 identified 90 % of these cases, whereas PSA detected 74 %. The investigators reported that the number of false-positive results—men classified as high-risk without aggressive disease—was comparable for the two tests.
Background: Limitations of PSA Screening
Since the 1990s, PSA testing has been the dominant screening tool despite well-documented limitations. Conventional PSA screening often leads to invasive and costly follow-up procedures, contributes to the over-diagnosis of indolent cancers, and misses a substantial proportion of aggressive disease.
Key Researchers and Developers
- Thorgerdur Palsdottir, Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Sweden – lead researcher on the study.
- Hari Vigneswaran, MD, Chief Medical Officer, A3P Biomedical – co-author of the study and spokesperson for the test’s developer.
- A3P Biomedical – company that created the Stockholm3 assay.
- Karolinska Institutet – academic institution where the trial was conducted.
Data Highlights
- Cohort size: >12,000 men (ages 50-74).
- Aggressive cancers diagnosed: 443.
- Detection rates: Stockholm3 = 90 %; PSA = 74 %.
- False-positive rates: Similar for both tests (exact percentages not disclosed).
- Missed aggressive cancers: Significantly fewer with Stockholm3 than with PSA.
Official Statements & Responses
Palsdottir emphasized that distinguishing truly dangerous prostate cancers remains a major screening challenge and that Stockholm3 “identifies significantly more aggressive cancer cases than PSA without increasing the number of unnecessary follow-ups.” Vigneswaran highlighted the clinical importance of early detection, noting that five-year survival approaches 100 % when aggressive disease is confined to the prostate. He also stated that the test could reduce unnecessary MRIs and biopsies. Although promising, Vigneswaran clarified that Stockholm3 is still investigational, not yet available in the United States, and that a biopsy remains required for definitive diagnosis. A3P Biomedical intends to pursue FDA approval and generate U.S. data to support routine screening use.
Criticism, Limitations, and Gaps
- Investigational status: Stockholm3 is not approved for sale or clinical use in the U.S.
- Need for confirmatory biopsy: The assay estimates risk but does not replace tissue diagnosis.
- Population scope: Study participants were primarily Swedish or European, limiting immediate generalizability to other ethnic groups.
- Evidence gap: U.S. data are absent, and regulatory clearance has not been obtained.
- False-positive equivalence: While rates are reported as similar, precise metrics are not provided, leaving uncertainty about comparative specificity.
Verbatim Quotes
- “Our results show that Stockholm3 identifies significantly more aggressive cancer cases than PSA without increasing the number of unnecessary follow-ups,” — Thorgerdur Palsdottir, researcher, Karolinska Institutet
- “These results point toward a potential change in how prostate cancer screening can be conducted,” — Thorgerdur Palsdottir, researcher, Karolinska Institutet
- “ "It leads to invasive and costly follow-up testing, contributes to over-diagnosis of non-aggressive cancers and, most importantly, it misses a substantial share of aggressive disease," Vigneswaran said.” — Hari Vigneswaran, MD, chief medical officer, A3P Biomedical
- “ "The goal of screening is to find the cancers that need treatment while they are still curable, without raising the number of men who screen positive but don’t have aggressive disease," he said.” — Hari Vigneswaran, MD
- “When aggressive prostate cancer is found while still confined in the prostate, the five-year survival rate is close to 100%, which highlights the importance of early detection, according to the doctor.” — Hari Vigneswaran, MD
Future Outlook
A3P Biomedical plans to submit the Stockholm3 assay for FDA review and to conduct U.S. studies that will provide the evidence required for regulatory approval. If approved, the test could streamline prostate-cancer screening by reducing reliance on MRIs and biopsies while improving detection of clinically significant disease.
