Gene Test May Predict Prostate Cancer
Study Shows Experimental Blood Test May Be More Accurate Than PSA Test
June 2, 2009 (Orlando, Fla.) -- A blood test that characterizes each prostate tumor by its unique genetic fingerprint may help pinpoint which men actually have prostate cancer, researchers say.
In a new study, the powerful genetic tool beat out standard PSA testing in discriminating between men who had cancer and those who did not, says Robert Ross, MD, of the Dana-Farber Cancer Institute in Boston.
PSA levels are a measure of a protein called prostate-specific antigen, which is produced by cells in the prostate. High PSA levels can signal cancer.
The new test, which looks at the activity of six genes involved in prostate cancer, was described at the annual meeting of the American Society of Clinical Oncology.
Men whose PSA levels signal a high chance of prostate cancer typically undergo a biopsy, but 60% of these biopsies turn out to be negative, Ross says.
"Each year in the U.S., over 1 million men undergo the anxiety and pain of prostate biopsies at a considerable psychological cost," he tells WebMD.
The hope is that a new genetic test can help men avoid the pain, discomfort, and anxiety of unnecessary biopsies, Ross says.
Six-Gene Test for Prostate Cancer
For the study, which employed a commercially available gene chip, the researchers started with a set of 392 genes that had been associated with cancer.
Using blood samples from 76 men with prostate cancer and 76 healthy men, the researchers homed in on six genes whose activity was significantly associated with prostate cancer. The technique was then validated on blood samples from 128 men with prostate cancer and 84 who didn't have the disease.
"We found that the six-gene test correctly classified 86% of men with the disease," Ross says. In contrast, PSA testing was correct only 70% of the time.
When the gene test and PSA were used in combination, researched achieved the best results of all.
The results are a "significant improvement" over PSA alone, Ross says.
The next step will be to see if the gene test correctly predicts biopsy results in a 1,000-patient study.
Howard Sandler, MD, a prostate cancer specialist at Cedars-Sinai Medical Center in Los Angeles, tells WebMD that PSA testing "is incredibly valuable" for prostate cancer screening.
The gene screen "could be another test that helps to improve early prostate cancer detection," he says.
"But the problem with all these tests is their inability to answer the question we really want to know: Do you have potentially lethal cancer or do you have cancer that will never kill you?" Sandler says.
Sandler is referring to the fact that many prostate tumors grow so slowly that some men are likely to die from other causes long before the tumor itself becomes deadly.
Ross says the test may be able to distinguish between slow and faster growing cancers, but that further testing is needed before that claim can be made.
The study was supported in part by Source MDx, which developed the new test.