17 December 2010
Researchers in Iceland say they've developed a more effective test to screen for prostate cancer.
In many countries, prostate cancer is among the leading causes of cancer deaths in men. Doctors rely on a blood test called PSA (prostate-specific antigen) to screen for the disease. But there are big problems with the PSA test. Now, the researchers in Iceland report having a genetic tweak that will make PSA results a much better indicator of prostate cancer.
Prostate cancer can develop even when PSA scores are in the normal range. Likewise, men with high PSA levels can be completely free of disease. Genetics researcher Kári Stefánsson says the problem is that there's really no such thing as a "normal" PSA level that applies to all men.
"Among normal men - men without any disease in their prostate - there is considerable difference in how high their normal PSA level is. And we managed to find genetic markers that allow us to classify men into those who normally have high PSA, and those who have normally low PSA."
Stefánsson is the CEO of deCODE Genetics, in Iceland, and was earlier on the medical school faculties of the University of Chicago and Harvard. He says adding genetic information to the PSA score personalizes the prostate cancer test.
"So you may actually be a man who was born with naturally very low PSA, and you could actually double your PSA level because you have cancer, and it would still be read as normal. So what we have now is a test that allows us to control for all of this."
Stefánsson and his colleagues describe the new genetic supplement to the PSA test in the journal Science Translational Medicine.
For their study, they used genetic samples from about 2,500 men in Iceland and Britain. Iceland's population is famously homogeneous, and the British component was mostly men of European descent, which raises the question of how reliable the results would be for men of other ethnic groups. Stefánsson acknowledges the issue.
"Most of the drugs on the market today have been developed by doing clinical trials in people of European descent. So there is always a bit of a concern that some of them may work less well for people of other ethnic backgrounds, and the same thing applies to diagnostic instruments."
That may be especially true for Africans and men of African descent, he said, because they have higher rates of prostate cancer and die more often of the disease.
Kári Stefánsson of deCODE Genetics says the genetic supplement to the PSA test could be on the market as soon as next year.