Stockholm3 Blood Test Outperforms Standard PSA Screening for Prostate Cancer Detection: Study
Sweden: A secondary analysis of a randomized trial found that the multicomponent blood-based Stockholm3 test, which combines prostate-specific antigen (PSA), additional plasma protein biomarkers, a polygenic risk score, and clinical variables, detected more clinically significant prostate cancers while missing fewer cases than standard PSA screening.
Previous studies have also shown that combining the Stockholm3 test with an MRI-targeted biopsy approach reduces the overdiagnosis of prostate cancer without compromising the detection of clinically important disease. These findings support the use of the Stockholm3 test as part of a risk-adapted prostate cancer screening strategy.
Because PSA-based prostate cancer screening can lead to false-positive results, unnecessary biopsies, and missed clinically significant cancers, researchers evaluated the Stockholm3 test, which combines PSA with blood protein biomarkers, genetic risk, and clinical factors to improve screening accuracy.
In the study, published in the Annals of Internal Medicine, Thorgerdur Palsdottir, PhD, and colleagues from the Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden, conducted a secondary analysis of the prospective STHLM3-MRI randomized trial involving 12,670 men aged 50–74 years.
Men with abnormal PSA or Stockholm3 results underwent either systematic biopsy or MRI with systematic and targeted biopsies. The primary endpoint was the detection of clinically significant prostate cancer (grade group ≥2) within two years of screening.
The following were the key findings:
- During the 2-year follow-up, 443 of 12,670 men (3.5%) were diagnosed with clinically significant prostate cancer.
- Stockholm3 detected more clinically significant prostate cancers than PSA screening, while missing fewer cases.
- Stockholm3 achieved a 90% sensitivity, compared with 74% for PSA.
- The test maintained similar specificity to PSA (89% vs. 90%).
- Stockholm3 had a lower false-negative rate (10%) than PSA (26%), indicating fewer clinically significant cancers were missed.
- The false-positive rates were comparable between Stockholm3 (11%) and PSA (10%).
- Decision curve analysis showed that Stockholm3 provided greater clinical net benefit, with the potential to reduce unnecessary biopsies while improving the detection of clinically significant prostate cancer.
The findings suggest that combining multiple biomarkers, genetic risk, and clinical factors may improve prostate cancer screening by detecting more clinically significant cancers while reducing unnecessary diagnostic procedures.
The researchers acknowledged several limitations, including a participation rate of only about 25%, a follow-up period limited to two years, and a predominantly Swedish/European study population, which may limit the generalizability of the findings.
The researchers concluded that Stockholm3 provides greater clinical benefit than conventional PSA screening by detecting more clinically significant prostate cancers while reducing false-negative results. They emphasized the need for longer-term follow-up to confirm these findings and clarify the role of Stockholm3 in routine prostate cancer screening.
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