The University Record, January 28, 1997

More accurate test for prostate cancer can reduce invasive biopsies

From the U-M Medical Center


Researchers from the Michigan Prostate Institute of the University of Michigan and elsewhere have found a way to increase the sensitivity of the PSA (prostate-specific antigen) blood test. The findings will improve the detection of prostate cancer in its early, most curable stages and eliminate many of the unnecessary, invasive prostate biopsies done in this country every year.

The findings appear in the January issue of Urology.

"By having established when and how to use this new test, we can now find many more curable cases of prostate cancer and thus decrease the death rate from this disease," says Joseph E. Oesterling, director of the Michigan Prostate Institute, urologist-in-chief at the Medical Center, and an author of the report. "The regular old-fashioned PSA test is just not specific enough to always pick an early, curable cancer out of an ocean of benign conditions that also may be elevating the PSA level. This has caused us to miss cancers in their early stages and to do many unnecessary negative biopsies."

In the study, the Oesterling team studied hundreds of patients with prostate disease and found that the percentage of "free PSA" (one of several molecular forms of PSA) in patients with prostate cancer was lower than in those with benign disease. Using this information, they developed guidelines for the percentage of free PSA in the blood that corresponds to a strong likelihood of cancer.

With this added information, physicians can now detect cancer in men with PSA levels between 3 ng/ml and 4 ng/ml (traditionally, any PSA level below 4 was considered normal). Also, for men with levels between 3 and 10, these guidelines will identify whether the elevated PSA is due to cancer or a benign prostate condition that does not warrant biopsy.

Oesterling estimates that this new technique will enable physicians to detect 44 percent more early-stage prostate cancers and eliminate unnecessary prostate biopsies by 15 percent.

"This study has determined the correct situations for using percent-free PSA and has established its upper limits of normal. Ultimately this information will help save lives," Oesterling said.