Prostate cancer test may lower false positives by 75 per cent

A SCREENING tool for prostate cancer has been developed that could cut deaths and reduce the number of “false positives” by three quarters, research suggests.

Scientists from University College London created an algorithm that estimates the risk of developing the disease by examining two cancer markers in the blood. They hope it could be developed into a national screening programme if further studies are successful.

Prostate cancer is the most common form of cancer in men, with more than 50,000 diagnoses and 10,000 deaths each year in the UK.

There is no single test for prostate cancer but one of the first diagnostic tools used is a blood test that measures prostate-specific antigen (PSA).

But the test is not very reliable, as it finds too many “false positives”, where there is no cancer, or where it is growing so slowly that treatment is needless, while missing possibly harmful cases.

In a study, published in the Journal of Medical Screening, researchers developed an algorithm estimating the risk of developing prostate cancer based on age and the levels of two prostate cancer markers, PSA and hk2 (human kalliknein peptidase).

The study of more than 20,000 men tested how well the algorithm could predict prostate cancer by comparing blood samples of men who later died after a prostate cancer diagnosis with those who were never diagnosed with the disease.

They found that, by setting a risk threshold above which men are counted as “screen positive”, the approach would reduce the number of false positives by three quarters compared with a standard PSA test, while identifying the same proportion of cancers.

Prof Sir Nicholas Wald, lead author of the study from UCL’S Institute of Health Informatics, said: “Our study shows a different screening approach could reduce the number of false positives by three quarters. This would [reduce] over-diagnosis and over-treatment.”