Stockholm3, a prostate cancer test developed in Sweden, runs a combination of protein and genetic markers from a blood sample through an algorithm to find the probability of a patient having clinically significant cancer.

Studies in more than 90,000 men have shown that Stockholm3 produces significantly better results than the current PSA standard. The test improves prostate cancer diagnosis by reducing unnecessary MRI and biopsies and by identifying significant cancers in men with low or normal PSA values.

However, previous studies have been conducted primarily in Scandinavia on a mainly White population with uncertain generalisability to the rest of the world. A Swedish-American research group has now examined how well it works in an ethnically mixed group of men in the USA and Canada.

The study included over 2,000 men at 17 different clinics, 16 per cent of whom were Asian, 24 per cent African-American, 14 per cent Latin American and 46 per cent White American. All participants had a referral for a prostate biopsy on the basis of an elevated PSA score, abnormal rectal examination, MRI scan or other suspicious clinical finding.

Before the biopsy was performed, a blood test was taken along with clinical data pertinent to the Stockholm3 test, which was conducted blinded to the biopsy results.

The analysis shows that clinically relevant prostate cancer cases were found in a total of 29 per cent of the men, somewhat more in African Americans and slightly fewer in Asians. It also shows that the Stockholm3 test could almost halve the number of unnecessary biopsies (45 per cent fewer: 673 as opposed to 1,226) while being no less effective at detecting all clinically relevant cases. The results were similar across the different ethnic groups.

“The study demonstrates that the Stockholm3 test is just as effective on an ethnically mixed group as it is on a White, Swedish population,” says the study’s lead author Hari T. Vigneswaran, doctor and PhD student at the Department of Medical Epidemiology and Biostatistics, Karolinska Institutet.

According to him, the research answers several important questions and will lead to a more widespread use of the method:

“Colleagues in other countries are very interested in these data, which show that Stockholm3 works for a non-Swedish population and among minorities.”

The study was financed by the Swedish Research Council, the Swedish Cancer Society and A3P Biomedical, the company that holds the rights to the development of the Stockholm3 test. Hari T. Vigneswaran and Thorgerdur Palsdottir are employed at A3P Biomedical. Co-authors Henrik Grönberg, Martin Eklund and Tobias Nordström hold shares in A3P Biomedical AB. Henrik Grönberg and Martin Eklund are inventors of patents for the method. Other co-authors report research grants and fees from a number of pharmaceutical companies unrelated to the Stockholm3 method.