A3P Biomedical's Stockholm3 outperforms PSA in 12,670-man study

A3P Biomedical has published results from a population-based screening study of 12,670 men comparing its Stockholm3 blood test against conventional PSA screening for aggressive prostate cancer, with data appearing in the Annals of Internal Medicine. The Swedish diagnostics company says the study represents one of the largest prospective datasets yet compiled for an alternative prostate cancer screening approach.

The STHLM3-MRI study enrolled men aged 50 to 74 and tracked outcomes over two years via linkage to the Swedish National Cancer Registry. Stockholm3 achieved a sensitivity of 90% for detection of Grade Group 2 or higher prostate cancer, compared with 74% for PSA at a threshold of 3 ng/ml and 52% for PSA at the more commonly used threshold of 4 ng/ml. False-positive rates were similar for Stockholm3 and PSA at 3 ng/ml, at 11% and 10% respectively, while PSA at 4 ng/ml produced a lower false-positive rate of 5% but at the cost of missing nearly half of men with clinically significant disease.

The clinical case against PSA

The sensitivity gap is the crux of the clinical argument. A test that misses approximately half of aggressive cancers at the standard 4 ng/ml threshold is widely accepted to be inadequate, and the field has spent two decades searching for a more reliable first-line triage tool. David Grossman, former chair of the US Preventive Services Task Force, noted in comments accompanying the release that while the adoption of pre-biopsy MRI has reduced unnecessary biopsies, PSA's poor sensitivity for aggressive disease has remained a persistent limitation. "These data suggest that Stockholm3 offers the potential to improve detection of clinically significant prostate cancers without increasing false negatives," Grossman said.

Martin Steinberg, chief executive of A3P Biomedical, described the publication as part of a growing evidence base now spanning more than 90,000 men across more than 40 peer-reviewed publications. The company is positioning Stockholm3 as a candidate first-line screening test, though the product remains classified as an investigational device in the United States and is not yet approved for commercial sale there.

Market context and regulatory path

Prostate cancer diagnostics is a competitive and commercially significant space. The US records more than 300,000 new cases annually, and approximately 36,000 men are expected to die from the disease in 2026 according to the company's own figures, most attributed to aggressive tumours not caught early by PSA. That unmet need has attracted a range of diagnostic developers, including companies pursuing liquid biopsy approaches, genomic risk classifiers such as Decipher and Oncotype DX Genomic Prostate Score, and multivariate blood panels.

Stockholm3's combination of PSA, additional protein biomarkers, a polygenic risk score, and clinical variables in a single algorithm is intended to address a known weakness of single-marker approaches. However, moving from published evidence to regulatory clearance and reimbursement in the US market will require engagement with the FDA on the investigational device pathway and, ultimately, a health economics case to payers that the improved sensitivity justifies any uplift in cost over existing tests.

Kevin Oeffinger of the Duke Cancer Institute, who is a current member of the American Cancer Society Guideline Development Group, described the trial as "a large-scale, high-quality" study and suggested it could represent a turning point for prostate cancer screening. A3P Biomedical has not disclosed a timeline for a US regulatory submission.