New Prostate Cancer Tests on the Horizon

www.ohsu.edu | 07.26.2010

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.

Testing for Prostate Cancer with Genes
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.

Biomarkers Help Find Cancers
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 U.S. 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.

Testing for Prostate Cancer
Diagnosing prostate cancer is often a multi-step process. In addition to a complete medical history and physical examination, diagnostic procedures for prostate cancer may include the following:

DRE (digital rectal examinations) - usually conducted annually for men over the age of 50.

PSA (prostate-specific antigen) and PAP (prostatic acid phosphatase) - these blood tests are usually conducted annually for men over the age of 50. Men in high-risk groups, such as African-Americans, or those with a strong family history of prostate cancer, should consult their physicians about being tested at age 45.

If the DRE or PSA are unusual, other evaluation tools may include:

transrectal ultrasound (TRUS) - a test using sound wave echoes to create an image of the prostate gland to visually inspect for abnormal conditions such as gland enlargement, nodules, penetration of tumor through capsule of the gland, and/or invasion of seminal vesicles.

computed tomography scan (also called a CT or CAT scan) - a diagnostic imaging procedure that uses a combination of x-rays and computer technology to produce cross-sectional images (often called slices), both horizontally and vertically, of the body.

magnetic resonance imaging (MRI) - a diagnostic procedure that uses a combination of large magnets, radiofrequencies, and a computer to produce detailed images of organs and structures within the body.

radionuclide bone scan - a nuclear imaging method that helps to show whether the cancer has spread from the prostate gland to the bones.

lymph node and/or prostate biopsy - a procedure in which tissue samples are removed (with a needle or during surgery) from the body for examination under a microscope to determine if cancer or other abnormal cells are present.

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