Tests Might Diagnose, Predict Prostate Cancer

By Steven Reinberg
26 feb 2009-- One study suggests that a simple urine test could pick out 50 percent of men with prostate cancer. Another study says that combining risk factors for prostate cancer may help predict the likelihood of developing the disease.

Both studies were presented Tuesday at the 2009 Genitourinary Cancers Symposium in Orlando, Fla., sponsored by the American Society of Clinical Oncology, the American Society for Radiation Oncology, and the Society of Urologic Oncology.

"Current methods for diagnosing prostate cancer -- PSA (prostate-specific antigen) and digital rectal exam -- have low specificity," lead researcher Jack Groskopf, a senior research scientist for Gen-Probe Inc., in San Diego, said during a Tuesday teleconference. "As a result, the majority of prostate biopsies are negative, and you could argue that we are doing too many biopsies."

There is a need for a better test and a better way to determine which men need aggressive treatment and which men need only monitoring, Groskopf said.

Toward these ends, Groskopf's team developed a urine test that can identify particular gene fusions associated with prostate cancer. The gene fusions involve the TMPRSS2 gene and the ERG gene. This particular fusion is found in about 50 percent of men with prostate cancer and can be identified in urine, Groskopf said.

"This is an ideal target for a diagnostic test," he said. "Another exciting aspect of the gene fusions is that they potentially provide an explanation for the progression of prostate cancer."

Using their test in 556 men before they underwent a biopsy, the researchers found the exam had a "specificity" for prostate cancer of 84 percent, compared with 27 percent for a PSA reading. The "sensitivity" of the test was 42 percent, but only half of men with the disease have this gene fusion, Groskopf noted.

The urine test also showed that it correlated well with other measures of gauging the aggressiveness of prostate cancer, Groskopf said.

In the second study, Dutch researchers used PSA readings, a family history of prostate cancer, the size of the prostate, and a previous negative biopsy to create a chart to predict the risk of developing prostate cancer.

The researchers tested their formula in 5,176 men who were screened for prostate cancer after four years. "PSA is still the most significant predictor, but there are other factors that also contribute risk," Monique J. Roobol, who's with the Department of Urology at the Erasmus Medical Center in Rotterdam, said during the teleconference.

The overall risk of developing prostate cancer was 5.1 percent, Roobol said. Men whose PSA levels were 1.5 nanograms per milliliter were seven times more likely to develop prostate cancer than men with a lower PSA, she said.

A family history of prostate cancer will increase the risk of the disease, as will having a small prostate, Roobol said. But if you have had a negative prostate biopsy, your risk decreases, she noted.

Men who have higher risk factors may need more frequent screening, Roobol said. "Men below this threshold may need less frequent screening," she added.

Dr. Durado Brooks, director of colon and prostate cancer prevention programs at the American Cancer Society, doesn't think either of these studies will change clinical practice anytime soon.

Discussing the first study, Brooks noted that this gene fusion is only found in half of prostate cancers. "If you don't find it, it doesn't mean prostate cancer isn't there," he said. "From a screening standpoint, this test is not likely to be very helpful at all."

As for the second study, Brooks said he wasn't sure that integrating these risk factors would effect patient treatment. "This is interesting, but I don't see how this is going to alter practice," he said.

A third study presented Tuesday looked at the benefit of using PET scans to diagnose bladder cancer. A research team led by Dr. Andrea B. Apolo, of Memorial Sloan-Kettering Cancer Center in New York City, compared PET scans with CT scans and MRIs to see which imaging technique was better at diagnosing the disease.

PET scans were more sensitive and specific in finding bladder cancer and distinguishing local from metastasized cancer, which is cancer that has spread to other sites in the body. In 68 percent of the cases studied, treatment plans were changed based on the results of the PET scans, the researchers said.

The researchers said these results argue for using PET scans as standard practice in diagnosing bladder cancer.