Avoiding Prostate Biopsy
New Approach Predicts When Invasive Test Not Needed
Oct. 15, 2002 -- Diagnosing prostate cancer means needle biopsies. Three-fourths of the time, no cancer is found. Now, a new test promises a vast reduction in needless needling.
It's called the proteomic profile. Proteomics is the study of proteins -- the building blocks of life. Proteins make up the tissues of the body. They also make up the chemical language that the cells of the body use to communicate with one another.
This language carries detailed information on the state of our health. It's not yet possible to understand most of it. But this language looks different when a person is sick than it does when a person is healthy. The problem with seeing the exact difference is that there are thousands and thousands of proteins to look at.
The solution: a sophisticated computer program similar to one used decades ago to uncover patterns of civil rights abuses. Using the program for medical research is the brainchild of Peter J. Levine, JD, CEO of Correlogic Systems Inc.; Emmanuel F. Petricoin III, PhD, co-director of the NCI/FDA Cancer Proteomics Program; and Ben A. Hitt, PhD, Correlogic chief scientific officer.
"We don't look for a needle in a haystack," Levine tells WebMD. "Instead we analyze the whole haystack to look for any change, however subtle, in how the pieces of hay are lying against one another."
Earlier this year these researchers used this patented Knowledge Discovery Engine to analyze the proteins circulating in the blood of women with ovarian cancer and compare the pattern with that of healthy women. This led to a proteomic signature for ovarian cancer. From a few drops of blood it could tell -- with 94% accuracy -- whether a woman did or didn't have the disease. A larger, independent trial of the test is planned for 2003.
Now the Petricoin team has turned this technique to the problem of prostate cancer. Men with high blood levels of a prostate protein called PSA are at high risk of prostate cancer. Most men with a high PSA test have to get a prostate biopsy, yet two out of three times it turns out to be a false alarm. Could a proteomic profile help?
Reporting in the Oct. 16 issue of the Journal of the National Cancer Institute, the researchers find that the test correctly predicted prostate cancer in 36 of 38 patients. It correctly said there was no cancer in nearly eight out of 10 cases. Perhaps most significant were the findings for men whose PSA test was hard to interpret -- those with marginally elevated PSA scores. Nearly all of such men opt for biopsies. The proteomic test could tell with more than 70% accuracy whether they had cancer or not.
Prostate specialist Mark S. Litwin, MD, MPH, associate professor of Urology at UCLA, says the test "heralds a new era in prostate cancer screening."