BOSTON (Reuters) - Researchers studying Swedish men say they have uncovered five genes responsible for nearly half of all cases of prostate cancer in that country and said their findings might lead to a better test for the disease.
Men having four of the five genes were 4.5 times more likely to develop a tumor than those who had none. For those who have all five genes and a family history of prostate cancer, the risk was 9.5 times greater.
The researchers, who report their results in the New England Journal of Medicine, say the findings are “significant and could affect clinical care” because a blood test can identify the cancer genes.
The team at Wake Forest University in North Carolina and Johns Hopkins University in Maryland drew blood from 2,893 prostate cancer patients and 1,781 men without the disease in Sweden.
They found 16 small changes in the genetic code that were more common to men with prostate cancer than those without the disease. Then they created a test using the most common of these changes, called single nucleotide polymorphisms or SNPs (pronounced ”snips).
Men with four or more of these SNPs were nearly 4.5 times more likely to be in the prostate cancer group, they reported.
“Our finding provides an opportunity to supplement the well-established risk factors by looking at how many of these variants a man has inherited,” Wake Forest’s Dr. Jianfeng Xu said in a statement.
“It may provide a much better weapon to guide clinicians,” Xu added.
Doctors now use a blood test for prostate-specific antigen or PSA to screen for prostate cancer, as well as physical exams, but both methods are far from perfect.
“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.
But in a commentary, Dr. Edward Gelmann of Columbia University Medical Center in New York said the benefits of any test would be limited because it would not distinguish between aggressive prostate cancer and cases that only need to be watched carefully.
Prostate cancer is often a slow-growing tumor and many men will die of something else before it becomes dangerous -- so “watchful waiting” is often prescribed.
Gelmann said a genetic test is unlikely to change anything among men who are already being monitored for the tumor, which will be diagnosed in more than 218,000 U.S. men this year and kills more than 27,000.
The researchers are planning to test DNA from U.S. men to see if the genes are linked to prostate cancer there as well.
Nearly 90 percent of Swedish men have at least one of the five telltale genes, and prostate cancer death rates tend to be 10 to 20 percent higher there than among U.S. whites, said Henrik Gronberg of the Karolinska Institute in Sweden, who also worked on the study.
Editing by Maggie Fox and Philip Barbara