A host of genome-wide studies has shown that a man's genetic makeup can predispose him to prostate cancer, currently the most common form of cancer in men other than skin cancer. Most older men will, in fact, eventually develop some lesions that would be clinically diagnosed as prostate cancer, even though a minority of those cases will turn out to be aggressive. But current screening techniques can rarely distinguish between the two, leaving some vulnerable to rapidly attacking cancers and others to unnecessary treatment.

Findings from a new study, published online today in the Proceedings of the National Academy of Sciences, might eventually help to improve this diagnostic step. Researchers have discovered a genetic variant that appears to make some men more likely to get an aggressive form of prostate cancer than the more frequent, slower variety.

This development will likely be a welcome advance. "Identifying factors that are associated with a risk of having or developing aggressive disease is urgently needed to reduce over-diagnosis and over-treatment of this common cancer," Karim Kader, a urologist at Wake Forest University School of Medicine in Winston-Salem, N.C, and study collaborator, said in a prepared statement. Previous studies have focused on genetic markers of overall risk for the cancer, which still kills more than 27,000 men in the U.S. each year. 

The study analyzed data from several different study populations in the U.S. and Sweden, assembling information on more than 17,000 men with prostate cancer. The researchers found that the frequency of genetic variant rs4054823 (the marker for the aggressive form) is "consistently different" between those with aggressive prostate cancer and those with slower forms of the disease.

The authors, however, are quick to note that the new marker is not likely to lead to a new method of testing just yet.

"A single variant with a moderate effect such as this is unlikely to be sufficient on its own at predicting risk," Jianfeng Xu, a professor of epidemiology and cancer biology at Wake Forest and lead study author, said in a prepared statement. "But its identification is significant because it indicates that variants predisposing men to aggressive disease exist in the genome…We believe it has the potential to one day be used in combination with other clinical variables and genetic markers to predict which men have aggressive prostate cancer."

The issue of prostate cancer diagnosis and screening has recently generated heated debate—especially after a March 2009 report showed that popular prostate-specific antigen (PSA) blood tests might not be saving as many lives as hoped. In fact, the randomized trial (published in the New England Journal of Medicine) found that annual PSA screening did not reduce the overall rate of death from the cancer.

The authors of the new study note that a genetic test might also be able to help doctors screen men more effectively based on determining who has a higher risk for more aggressive forms of the cancer. In the future, genetic tests could be conducted, Xu said, "at a stage when the disease is still curable"—or even before it appears.

Scan of prostate cancer courtesy of iStockphoto/jamesbenet