A new blood test may help address one of the key challenges in prostate cancer detection—identifying aggressive forms of the disease early on. According to research led by a team at Karolinska Institutet, the Stockholm3 blood test detected more clinically significant cancer cases than the well-established, but problematic, Prostate Specific Antigen (PSA) screening test.
The study appears in the Annals of Internal Medicine. Swedish researchers collaborated with teams from Europe and the U.S. on this work.
Prostate cancer is one of the top cancers among men globally, with an estimated 1.5 million new cases and 397,000 deaths annually. PSA testing has long been used for early detection. But, although PSA is prostate-specific, it is not cancer-specific. Elevated PSA levels can be caused by benign conditions as well as cancer and up to 50% of diagnosed aggressive prostate cancers are in men with low PSA values—below today’s cutoffs of PSA 3 ng/ml or PSA 4 ng/ml.
“There are a number of tests in development to improve on PSA alone. A lot of them, like Stockholm3, are fairly ingenuous and do a good job,” Mark Pomerantz told Inside Precision Medicine. He is a medical oncologist at the Dana-Farber Cancer Institute in Boston. Until one of these newer tests emerges as a winner, though, MRI is the gold standard for evaluating men with high PSA. “With MRI we can see the prostate in some detail,” Pomerantz said, “But it is expensive.”
The Karolinska-led researchers analyzed data from 12,670 men aged 50–74 from the population-based STHLM3-MRI study, which compared MRI-targeted and standard biopsy in men with elevated PSAs. In this more recent Annals study, the men were tested first with both PSA and Stockholm3 and followed for two years via national cancer registries, which allowed researchers to also identify cancer cases missed during the initial screening.
Stockholm3 detected 90 percent of aggressive cancer cases, compared to 74 percent for PSA.
“The test incorporates plasma protein biomarkers, genetic risk information from a polygenic risk score, and clinical factors such as age, family history, and prior biopsy history,” the study’s lead author Thorgerdur Palsdottir, told Inside Precision Medicine. Palsdottir is a researcher at the Department of Medical Epidemiology and Biostatistics, Karolinska Institutet.
He added, “Together, these components provide a more comprehensive estimate of a risk of harboring clinically significant prostate cancer than PSA alone.”
The components, he explained, map onto distinct biological axes rather than a single one. The kallikreins (PSA, free PSA, hK2) reflect prostate epithelial and tumor secretory activity, and the free-to-total PSA relationship helps separate benign enlargement from cancer. The polygenic score and family history capture inherited susceptibility—a man’s baseline predisposition—rather than anything about a tumor. GDF-15 is a stress-response marker that has been associated with more aggressive disease across several cancers.
During the study follow-up, 443 men were diagnosed with clinically significant, i.e. aggressive, prostate cancer. Stockholm3 missed significantly fewer serious cancer cases than PSA, while the proportion of men incorrectly classified as high-risk was similar between the tests.
“These results point toward a potential change in how prostate cancer screening can be conducted. A more precise blood test could enable earlier detection of aggressive disease while reducing the number of unnecessary follow-up examinations and procedures,” said Palsdottir.
He adds that longer-term follow-up is needed to fully assess the effects on mortality and long-term outcomes. “The next important step is to evaluate longer-term outcomes, including disease progression, metastatic disease, and prostate cancer mortality.”
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