New Test Identifies Most Dangerous Prostate Cancers

A new way of measuring the aggressiveness of prostate cancer could someday cut in half the number of men with the disease who have their prostates surgically removed.

Whether a man with prostate cancer needs a prostatectomy often hinges on what is called his Gleason score, a test that grades the tumor based on its appearance under a microscope. The Gleason score, which has been used for decades, determines how advanced the cancer is, grading the malignancy on a score of 2 to 10. If the score is 6 or higher, the physician is likely to perform a prostatectomy, removing the entire gland.

A prostatectomy is done to save lives, but it is an unpleasant experience because one of the possible adverse effects is impotence.

But researchers at the University of Minnesota, where Dr. Donald F. Gleason first developed the test, have come up with a new test that could single out those who would benefit from a prostatectomy from those who would not necessarily need the operation.

New Prostate Cancer Test Hold Promise

The new test determines how aggressively the cancer is growing and spreading through the body. Its assessment is based not on the appearance of cancer cells but on their biochemistry, Gleason says. It is actually two interlocked tests, measuring levels of two molecules produced by the cancer cells.

"One is an enzyme called cathepsin B," says the study's lead author, Akhouri A. Sinha, a professor of genetics, cell biology, and development at the University of Minnesota Cancer Center. "It is produced in every solid tumor and has the ability to dissolve connective tissue, which stimulates spread of the cancer throughout the body.

"I have also looked at an inhibitor of cathepsin B, stefin A. What we have done is to take the ratio of cathepsin B to stefin A. If the ratio of cathepsin B to stefin A is high, the cancer is likely to grow and spread aggressively. This provides an excellent test to predict the progression of the cancer," he adds.

New Test Yields Positive Results

Sinha and his colleagues at the university and the Minneapolis Veterans Affairs Medical Center ran the test on 97 men whose prostate cancers graded 6 or higher on the Gleason test. They found an excellent correlation between the ratio of the two molecules and the progression of the disease, with differences among men whose Gleason scores were identical.

One existing way to judge a prostate cancer is to measure levels of prostate-specific antigen, PSA. If those levels rise after the prostate is removed, the chance of a recurrence is high. The new test predicted such recurrences before PSA levels rose, Sinha says.

What This Means For the Future of Prostate Cancer Treatment

What he sees in the future is use of the new test for all men with prostate cancer. "You can take a small biopsy and do the test in the hospital," he says. "Any competent clinical laboratory can do it."

And, more important, he adds, "If 100 men are diagnosed with a Gleason score 6, now all the prostates come out. Our projection is that 50 to 52 percent of them should not have a prostatectomy, because they do not have aggressive tumors. They can play golf and enjoy their lives. The others should have their prostate cancers treated very aggressively, because the tumors are likely to return in less than five years."

But the newly reported study is just the first step toward that future, Sinha says. "What we need to do now is a prospective study to correlate results with biopsy data. We are hoping that someone will want to do it, and we will help to set it up."

Discussions about such a study have already begun with researchers at another institute, Sinha says.

Gleason, who is an emeritus professor of pathology at Minnesota, is listed among the authors of the study, which is published in the journal Cancer. But he cheerfully admits, "I was lucky to have my name attached to it."

Retired for several years, he acknowledges that the Gleason test "made me famous. It is in use all over the world -- Russia, China, Japan."

Always consult your physician for more information.