Prostate Cancer Risk Testing: Stockholm3® and Proclarix® Explained

What is prostate cancer risk testing?

Prostate cancer is the most common cancer in men in the UK, with around 52,000 new cases diagnosed each year. Like many cancers, the earlier it is detected, the better the outcomes, but detecting it accurately is not always straightforward.

Risk testing for prostate cancer refers to a group of diagnostic tools designed to help clinicians assess how likely it is that a man has prostate cancer, and specifically, whether he has a form that requires further investigation or treatment. These tests are typically used before a biopsy is considered, helping to ensure that the right men are referred for further investigation, and that unnecessary procedures are avoided where possible.

What is PSA, and why isn’t it enough on its own?

Prostate-specific antigen (PSA) is a protein produced by the prostate gland. A blood test measuring PSA levels has been widely used for decades as an early indicator of potential prostate cancer. However, PSA alone has limitations.

An elevated PSA level does not necessarily mean a man has prostate cancer. PSA can be raised by several non-cancerous conditions, including benign prostatic hyperplasia (an enlarged prostate), prostatitis (inflammation of the prostate), or even recent physical activity. As a result, relying on PSA alone sometimes leads to unnecessary biopsies, an invasive procedure that carries its own risks, while also missing some clinically significant cancers.

For this reason, advanced prostate cancer risk stratification tests have been developed to give clinicians a more accurate and complete picture before decisions are made around further investigation.

What is Stockholm3®?

Stockholm3® is a multi-analyte blood test that combines several different types of biological information to produce a personalised risk score for clinically significant prostate cancer. In a large prospective screening study, Stockholm3® demonstrated 90% sensitivity for detecting aggressive prostate cancer. This performance significantly outperforms PSA thresholds at comparable specificity.

It analyses protein markers in the blood alongside a genetic risk score derived from genetic markers, specifically, single nucleotide polymorphisms (SNPs) associated with prostate cancer risk, as well as clinical variables including age, family history, and previous biopsy results. This combination gives Stockholm3® a uniquely comprehensive picture of a man’s underlying prostate cancer risk, including any genetic risk.

Stockholm3® is particularly well suited for:

• Men with a family history of prostate cancer: the genetic component of Stockholm3® makes it specifically well suited in these cases.
• Men who have had a previous negative biopsy: Stockholm3® is validated for men who continue to have elevated PSA or clinical suspicion following a prior negative biopsy. The broader biological picture, including genetic risk, provides additional context that protein markers alone cannot.
• Men from ethnically diverse backgrounds: uniquely among advanced prostate cancer risk tests, Stockholm3® has been prospectively validated across Asian, Black, Hispanic, and White populations. The SEPTA trial confirmed consistent performance across all four ethnic subgroups, with unnecessary biopsy reductions of 42–52%.
• Men with PSA values between 1.5-20 ng/mL, where comprehensive risk stratification is the priority.

What is Proclarix®?

Proclarix® is a protein-based blood test that uses a panel of biomarkers (THBS1, CTSD, PSA, free PSA) to generate a risk score for clinically significant prostate cancer. Unlike Stockholm3®, Proclarix® does not include a genetic component. Instead, it focuses on what is measurable in the blood at the time of testing, providing a focused and clinically actionable answer to the pre-biopsy question. In a large prospective multicentre study, Proclarix® demonstrated 91% sensitivity for detecting clinically significant prostate cancer in men with PSA in the 2–10 ng/mL grey zone – significantly outperforming free PSA ratio and the ERSPC risk calculator at comparable specificity, while reducing unnecessary biopsies by 22%.

Proclarix® is particularly well suited for:

• Men with PSA 2–10 ng/ml, enlarged prostate (≥35cm³), and normal digital rectal examination: the core validated population from the PROPOSe study, representing a very common and clinically challenging presentation where Proclarix® performs significantly better than PSA alone, free PSA ratio, and standard risk calculators.
• Men with PI-RADS 3 MRI findings: where the biopsy decision is equivocal following MRI. Proclarix® has been shown to outperform PSA density in this subgroup and provides additional discriminatory value supporting a clearer clinical decision.
• Both biopsy-naïve and repeat biopsy patients: Proclarix® has been validated in both settings and was the only independent predictor of clinically significant prostate cancer on multivariate analysis, regardless of prior biopsy status.
• Men where a focused, protein-based risk score is the clinical priority: particularly in primary care settings where a clear and interpretable result is needed to support a timely biopsy decision.

Stockholm3® vs Proclarix® – at a glance

Both tests are validated tools to complement PSA testing. Both aim to reduce unnecessary biopsies while maintaining high sensitivity for clinically significant prostate cancer. The key distinction lies in the biological question each test is designed to answer.

	Stockholm3®	Proclarix®
Test Type	Multi-analyte: 5 protein biomarkers + 101 genetic markers + clinical variables	Protein-based: PSA, free PSA, THBS1, CTSD + clinical variables
Genetic Component	Yes – includes polygenic risk score (SNPs)	No – focused on protein biomarkers at time of testing
Indicated Population	Men aged 45–74, PSA between 1.5-20 ng/mL, no prior diagnosis	Men with PSA 2–10 ng/mL, prostate volume ≥35 ml, normal DRE, no prior diagnosis
Results Format	High Risk / Normal Risk / Low Risk with recommendation	Risk score 0–100%; cut-off at 10%
Guideline Status	CE-marked; validated across Asian, Black, Hispanic and White populations	CE-IVDR certified; EAU 2026 and AUA/SUO 2026 guidelines
Particularly Suited To	Family history, previous negative biopsy, diverse ethnicities, comprehensive long-term risk profiling	PI-RADS 3 post-MRI, biopsy-naïve and repeat biopsy patients, focused pre-biopsy decision support

How do I access Stockholm3® or Proclarix® through Source BioScience?

Both Stockholm3® and Proclarix® are available through Source BioScience. We provide clinicians and healthcare providers with access to both tests, alongside the clinical data and evidence base needed to make informed decisions for their patients.

Source BioScience does not advise on which test is right for an individual patient; that decision belongs to the clinician. Our role is to provide accurate, unbiased information about both tests and deliver a high-quality laboratory service once the clinical decision has been made.

If you are a healthcare professional interested in offering Stockholm3® and Proclarix® to your patients, please contact our team to find out more about the tests and how to access them through Source BioScience.