Blood Biomarkers After an Elevated PSA: What GOTEBORG-2 Showed for the 4Kscore

An elevated PSA is a starting point, not a diagnosis. In the GOTEBORG-2 prostate cancer screening trial, adding a 4Kscore blood test as a reflex step after an elevated PSA would have spared many men an MRI and a biopsy, and would have reduced the diagnosis of low-grade cancers that rarely need treatment. The same step would have delayed an intermediate-grade diagnosis in a small number of men. That is the trade-off the trial was built to measure, and it deserves a careful reading before anyone treats a single PSA number as a verdict.

What a reflex biomarker is trying to solve

PSA is a useful screening trigger and a poor stopping point. A value at or above the common 3.0 ng/ml threshold sends a man down a pathway that, in modern protocols, runs from PSA to MRI to targeted biopsy. Much of that downstream work lands on men who either have no cancer or have a low-grade cancer that would never have harmed them. The imaging, the biopsies, and the label of cancer all carry cost, anxiety, and occasional harm.

A reflex biomarker is a second, more specific blood test run automatically when PSA is elevated, before imaging or biopsy. The idea is to act as a gatekeeper: keep moving forward the men whose biology looks concerning, and hold back those whose risk of clinically significant cancer is genuinely low. The 4Kscore combines four kallikrein markers (total PSA, free PSA, intact PSA, and human kallikrein 2) with clinical variables into a single percentage risk of aggressive prostate cancer. GOTEBORG-2 asked what would have happened if that score sat between the PSA result and everything that follows.

What GOTEBORG-2 actually tested

GOTEBORG-2 is a population-based randomized screening trial in Sweden that invited roughly 38,000 men aged 50 to 60. The 4Kscore analysis, published by Andreas Josefsson, Marianne Mansson, Kimia Kohestani, and colleagues in European Urology in 2024 (volume 86, pages 223 to 229), was a prespecified, blinded sub-study. It focused on men with PSA at or above 3.0 ng/ml who had an evaluable MRI and, where indicated, targeted biopsy results, several hundred men in all. Blood already collected at screening was used to calculate a 4Kscore, and the investigators modeled what would have changed if a 7.5 percent cutoff had been used to decide who proceeded to MRI.

This design matters for how much weight the results can carry. The comparison is a within-trial modeling of a real screened cohort against its own actual pathway, not a separate randomized arm in which men were prospectively managed by their 4Kscore. That makes the estimates credible and internally consistent, while still leaving the true long-term outcomes, such as metastasis or mortality, unmeasured in this analysis.

The numbers, and what they mean

Expressed per 1,000 men with an elevated PSA, applying the 4Kscore reflex at the 7.5 percent cutoff would have avoided MRI for 408 men, roughly 41 percent, and avoided biopsy for another 95 men, about a 28 percent reduction. It would have led to 23 fewer low-grade cancers being diagnosed, a 23 percent drop in the detection of Gleason Grade Group 1 disease. Those low-grade cancers are the ones most associated with overdiagnosis, because most are managed with active surveillance rather than treatment, and many would never have caused symptoms.

The test discriminated well. For intermediate-grade and high-grade cancer (Grade Group 2 or higher), the score reached an area under the curve of about 0.84, with a high negative predictive value at the chosen cutoff. In plain terms, a low 4Kscore was a fairly reliable signal that clinically significant cancer was unlikely at that moment.

The cost sits on the other side of the ledger. The same reflex step would have delayed the diagnosis of intermediate-grade cancer in four men per 1,000 with elevated PSA, about 4 percent of that group. Both of the intermediate-grade cancers falling below the cutoff in the analyzed sample were organ-confined Grade Group 2 disease at PSA values just above the threshold. Delay is not the same as a missed cancer, because these men would remain in a screening program and be retested, but it is a real trade and the trial names it plainly rather than hiding it.

How to hold this evidence

A few caveats keep the finding in proportion. The trial studied men aged 50 to 60 in a single high-participation Swedish screening program, so the exact percentages should not be transplanted onto older men, different ethnic populations, or opportunistic testing outside an organized program. The 7.5 percent cutoff is a chosen operating point, and moving it up or down slides the balance between avoided procedures and delayed diagnoses. And because this analysis models a diagnostic pathway rather than tracking cancer deaths, it tells us about biopsies, imaging, and grade at detection, not about lives changed decades later.

What GOTEBORG-2 does establish is a direction and a rough magnitude. A reflex kallikrein panel after elevated PSA can meaningfully shrink the amount of MRI and biopsy done, and can cut low-grade overdiagnosis, while shifting a small number of intermediate-grade diagnoses slightly later in time. Whether that trade is worth making is a judgment about how much a health system and an individual man weigh avoided procedures and avoided overdiagnosis against the discomfort of any delay.

This article is educational and is not medical advice; decisions about PSA follow-up, biomarkers, imaging, or biopsy belong to an individual and their own clinician. If your PSA comes back elevated, the useful takeaway is not a specific test to demand but a better question to ask: what does the number actually predict for someone like me, and what is the next step designed to rule in or rule out.