Test Detects Aggressive Prostate Cancer
May Also Be Used for Other Cancers
June 13, 2002 -- A simple new test may help determine which prostate cancer patients have a tumor that's more likely to spread to other organs -- and help doctors give the best treatment. And the test may eventually be able to predict the aggressiveness of other types of cancer.
Currently, the degree to which prostate tumors have progressed is determined by looking at the shape and appearance of the cancer cells under a microscope. The tumor is then given a score between 2 and 10 (with 10 being the most advanced cancer) -- called a Gleason score.
Men with a higher score have tumors at a more advanced stage of the disease, but the grading system does not take into account how fast the tumor is growing or spreading.
"That means that within any score, there are biologically aggressive and less aggressive forms of cancer," says study author Akhouri Sinha, PhD, professor of genetics and cell biology at the University of Minnesota Cancer Center, in a news release. "This makes it more difficult to predict outcomes for individual patients."
The new test, which Sinha developed along with the creator of the Gleason score, Donald Gleason, MD, PhD, takes into account two biological factors that help determine which tumors are more likely to spread.
To grow and break through surrounding healthy tissues, tumors produce an enzyme known as cathepsin B (CB), which destroys the proteins in the tissue that hold the cells in place. But at the same time, the cells also produce substances called stefins that act as CB's natural enemies and inhibit the destructive enzyme.
After analyzing tumor samples from 97 men with prostate cancer and eight men with noncancerous enlargement of the prostate, researchers found that the ratio of how much CB the tumor had in relationship to how much of the stefin it contained predicted whether the cancer had spread to one or more of the pelvic lymph nodes.
If the tumor had more CB than stefin, it was more likely to be aggressive and spread. But if the tumor had more stefin, it was less aggressive.
"The ratio of CB to stefin A reveals differences in tumors that are not visible under the microscope," says Sinha. "If this test were done on tumors of newly diagnosed patients, we would have an indication of which cancers were most aggressive, and we could give those patients aggressive treatment."