Gene test for prostate cancer shows promise

A cheap but powerful genetic test that can identify men with a high risk of developing prostate cancer - the commonest form of cancer in males - could soon be available according to US researchers. A study published in the New England Journal of Medicine suggests that the screening of just five genetic markers would be enough to alert medical staff to those at greatest risk of developing prostate cancer, invoking more rigorous screening and hopefully early detection of cancer.

Researchers based at Wake Forrest University School of Medicine in North Carolina, and John Hopkins University in Maryland, compared the genomes of 2893 Swedish men with prostate cancer and 1781 normal controls - looking for differences in their genomes. The genetic markers identified - termed SNPs (single nucleotide polymorphisms), - are single letter 'variants' within the genetic code.

Individually the variants carry only a small risk of prostate cancer and are commonplace within the general population. But when inherited together the researchers found that the risk was significantly greater, ranging from 4.5 times greater if men had four out of the five variants, to 9.5 times greater for men who had all five genes plus a family history of the disease. The five variants are thought to account for up to 40 percent of prostate cancer cases among the Swedish men studied, rising to a figure of 46 percent if a family history of the disorder was factored in.

Following the development of high-resolution genome screening techniques late in 2006, a host of whole genome association studies have been performed in disorders such as asthma, diabetes and autism. This study, however, is the first to tie several markers together to give a cumulative and significant association powerful enough to warrant immediate integration into disease management.

'When we considered the variants together we discovered their potential for predicting individual risk,' said Jianfeng Xu M.D. lead researcher at Wake Forrest. 'Because of the cumulative effects of these risk variants and family history, for the first time associations found through genome-wide screening appear to be useful in clinical practice.'

Presently prostate cancer screening involves using a blood test to measure levels of prostate-specific antigen (PSA) in the blood, as well as physical exams. The researchers hope that their test may improve the sensitivity of prostate cancer screening in Swedish men and are planning to test DNA from US men to see if the test would work there as well.

'A subset of men deemed to have a low risk of prostate cancer based on their PSA levels may in fact be at significantly elevated risk due to inheriting one or more of the genetic variants,' said Dr. Lilly Zheng, also of Wake Forest, which along with Johns Hopkins School of Medicine has patented the test.