A simple blood test might one day soon be able to determine which men are likely to develop prostate cancer.
Previous research has already found five gene flaws associated with prostate cancer risk. While each flaw, or variant, alone is moderately associated with the risk for prostate cancer, this new study found that when the variants are assessed together, they have a strong cumulative effect.
A man with four of the five variants has a 400 to 500 per cent increased risk of developing the disease compared to men with none of the variants, the researchers from the U.S. and Sweden found.
When a family history of prostate cancer is added to the equation - for a total of six risk factors -- a man with at least five of the six factors has an increased risk of more than 900 per cent.
The article will be published in New England Journal of Medicine.
The researchers came to their findings after analyzing DNA samples from 2,893 Swedish men with prostate cancer and 1,781 healthy men of similar ages; all were participants in a prostate cancer study in Sweden.
They found that each of the gene variants was fairly common in the population. But together, these five variants and a family history accounted for almost half (46 percent) of the prostate cancer patients the team studied.
The research team plans to sample DNA from U.S. populations of men to see if these genetic variants exist outside of Sweden.
If they do, the researchers think they could develop a simple blood test that would screen for these gene variants. Such a test could be highly useful, especially for men with a family history of prostate cancer or those who have a marginally elevated PSA (prostate specific antigen).
The researchers note, though, that the test would not be able to tell how aggressive a potential cancer may be.
"This information is not yet available as a genetic test for risk of prostate cancer, but efforts are under way to rapidly develop one," says William B. Isaacs, Ph.D., of the Johns Hopkins Brady Urological Institute, who participated in the study.
"While these findings need to be validated and refined, it's a step in the right direction to revealing the genetic-based reasons for this cancer that we have been looking for over the past 15 years," he added.
Currently, age, race and family history are the three factors associated with increased risk of prostate cancer. Family history is believed to account for about 10 per cent of prostate cancer cases.
Until last year, no specific genetic variants had been consistently identified as markers for prostate cancer risk. Then, advances in technology allowed researchers to take a more systematic approach to looking at the entire genome.
Through these searches, several research teams identified five genetic locations associated with risk of developing prostate cancer: three on chromosome 8q24, one on chromosome 17q12 and one on 17q24.3.
Each variant alone was associated with moderate risk, but the effect wasn't considered significant. This study was the first to evaluate whether there is a cumulative effect from having multiple variants.
The researchers said further study is needed to determine how genetic testing may complement PSA PSA testing.
