New Prostate Cancer Tests on the Horizon
Two new prostate cancer tests in development may offer added clues about which cancers require early treatment and which can be left for "watchful waiting," researchers reported at the recent annual meeting of the American Urological Association.
The tests can check for increased levels of genetic material. One test looks for the DNA of which genes are made, while the other test looks for the RNA that carries the messages from those genes. They show promise for cutting down on the number of biopsies now taken from men suspected of having prostate cancer.
Both tests appear to add certainty to the suspicion of prostate cancer provided by the most widely used test for prostate cancer, the prostate-specific antigen (PSA) blood screen.
PSA testing is often used to screen men for prostate cancer. A high blood level reading of PSA is often followed by a biopsy, or tissue sample, to detect cancer cells.
Dr. Rakesh Singal, at the University of Miami, presented one of the reports at the meeting. He says about one of three patients is likely to have a positive biopsy.
"We wanted to come up with a test that tells us which patients are likely to have positive biopsies," he says. This may help spare men unnecessary procedures and worry.
The test Dr. Singal described looks at blood levels of specific DNA. Prostate cancer can increase those levels because malignant cells grow abnormally fast and cause the death of other cells.
The study included 252 men referred for prostate biopsies because of abnormal PSA test readings. Dr. Singal's team found that high levels of the target DNA were linked closely with the presence of a cancer.
"What we think will probably happen in the future is that those men who have high PSA levels will have this test," says Dr. Singal. "If the DNA levels are high they will have biopsies; if low, they can be observed periodically."
But for that to happen, the results of this study have to be confirmed, he explains.
The other test, described by Dr. E. David Crawford, at the University of Colorado, is targeted to elevated levels of PCA3 "messenger RNA" in urine. Again, elevated levels of this genetic material are associated with the presence of a tumor.
According to Dr. Crawford, about a million biopsies are done in the US each year because of suspected prostate cancer. "Anything you can do to cut down the large number of biopsies has innumerable advantages," he says.
In the study, nearly 2,000 men with elevated PSA levels or abnormal results on a digital rectal examination (which measures prostate enlargement) also underwent PCA3 urine tests followed by biopsies.
The PCA3 readings were significantly higher in those men whose biopsies turned out positive for cancer, the team found.
In addition, "PCA3 level reflects the aggressiveness of cancer," says Dr. Crawford. The test could be used to single out prostate cancers requiring immediate surgery or radiation treatment.
Further studies are needed to determine whether PCA3 testing could serve that purpose, he says.
In the meantime, says Dr. Crawford, the immediate effect of the new study results is to help develop "a new paradigm" for early detection of cancer, in which PCA3 testing would go along with PSA testing and digital rectal examinations.
That combination could reduce the need for biopsies, which are expensive, cause discomfort, and are associated with a risk of infection, he says.
Always consult your physician for more information.
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